Quantity vocabulary

Use this reference when interpreting a dataset or adding a source record. Read The curated data for the record structure and Conventions for the package’s physical conventions. The tables below describe stored quantities, rather than the parameters of the model interfaces in the API reference.

Quantities

Every quantity belongs to a family, which is also the directory of its files: refractive (the real linear response and the dispersion it produces), absorption (cross sections and the oscillator-strength distribution), third_order, raman (the anisotropic and vibrational response, and the lines), ionisation, damage (laser damage and breakdown of solids), composition (the mole fractions of a gas mixture such as dry air; TC-543), transport (the dilute gas’s viscosity and the ideal gas’s heat capacity, OEP 1) and thermodynamic (the virial coefficients and densities of the gases and their mixtures, OEP 4). A quantity of a pair of gases is filed under the first of the pair in sorted order, with the other as parameters.partner; a mole fraction is always the material’s. A metal’s optical constants are refractive_index and extinction_coefficient, or permittivity_real and permittivity_imaginary where the source tabulates the permittivity. The vocabulary is optmat.vocabulary; the table below is checked against it (tests/test_datasets.py). “Needs state” applies to a gas; a solid has no state.

A solid’s datasets also state, in parameters, whenever the source does (TC-319):

• temperature_k, the temperature of the sample;

• form: bulk, film or fibre (a film’s deposition and thickness go in notes);

• grade: the product or melt as the source names it ("Corning 7940", "Suprasil 1", "Lithosil Q2");

• axis, for an anisotropic crystal: one of the material’s axes (see Materials);

• polarization, technique and pulse_fs for a nonlinear or damage measurement;

• index_medium for a refractive index (and its temperature coefficient): vacuum for an absolute index, air for one relative to the room air of the measurement (with air_temperature_k and air_pressure_pa where stated), or not stated (TC-398);

• assumed = true for a value a source takes as a model input (a band gap, a collision time, an effective mass in a simulation) rather than measures or derives. Such a value is use = "check", with reproduced_from where the source cites one.

form, site (bulk or surface), index_medium and an absorption coefficient’s base ("e" or "10") take only the values listed.

A gas’s datasets may also state, in free form:

• initial_state: the level a transition leaves, as the source labels it (for example "X 1Sigma_g+ (v = 0, N = 1), ortho-H2" for an ionisation energy);

• ortho_para: the ortho:para ratio of a hydrogen or deuterium sample ("3:1");

• temperature_range_k: a temperature range, where the source gives no single value ("296.0-298.5"). A model that needs one number takes it from the choices file (data/gas/raman.toml), which gives its reason.

Quantity	Family	Meaning	unit	Abscissae	Needs state	Required parameters	Extra columns
refractivity	refractive	n - 1 at the dataset’s state	1	wavelength	yes
polarizability	refractive	per-particle dipole polarizability; parameters.temperature_k for a temperature-dependent (rotationally averaged) value	SI, angstrom3, au, cm3	wavelength	no
molar_refractivity	refractive	A_R = N_A alpha / (3 eps0); parameters.temperature_k where stated	cm3/mol	wavelength	no
refractivity_per_density	refractive	(n - 1) / N at the dataset’s state	cm3	wavelength	yes
refractivity_ratio	refractive	(n - 1) of the gas over (n - 1) of parameters.reference_material at the same density	1	wavelength	no	reference_material
refractivity_difference	refractive	n(lambda) - n(parameters.reference_wavelength_nm) at the dataset’s state	1	wavelength	yes	reference_wavelength_nm
partial_refractivity	refractive	one stated contribution to n - 1 at the dataset’s state (parameters.contribution: what it is and how it was obtained)	1	wavelength	yes	contribution
polarizability_correction	refractive	a correction to the electronic polarizability (parameters.part, one of POLARIZABILITY_CORRECTIONS), never a total	SI, angstrom3, au, cm3	wavelength	no	part
magnetic_susceptibility	refractive	the diamagnetic (or paramagnetic) susceptibility: per particle (au, the magnetizability chi_0) or molar (cm3/mol, m3/mol: A_mu or chi_M)	au, cm3/mol, m3/mol	none, wavelength	no
cauchy_moment	refractive	dipole-oscillator-strength sum S(k), the order k as the abscissa	au	order	no
phase_match_density_ratio	refractive	density ratio rho_gas / rho_reference at which two gases phase-match a harmonic (parameters.reference_material, .harmonic)	1	wavelength	no	harmonic, reference_material
phase_match_density	refractive	density at which a harmonic is phase-matched against a stated mismatch (parameters.harmonic, .phase_mismatch_per_m)	as printed	wavelength	no	harmonic, phase_mismatch_per_m
phase_mismatch_per_density	refractive	wave-vector mismatch of a harmonic per particle, Delta k / N (parameters.harmonic)	as printed	wavelength	no
group_delay	refractive	group delay per unit length at the dataset’s state	fs/m	wavelength	yes
group_delay_dispersion	refractive	GDD per unit length at the dataset’s state	fs2/m	wavelength	yes
third_order_dispersion	refractive	TOD per unit length at the dataset’s state	fs3/m	wavelength	yes
dispersion_kappa	refractive	kappa = -lambda^2 d/dlambda[(n - 1)/lambda] at the dataset’s state	1	wavelength	yes
verdet_constant	refractive	Verdet constant at the dataset’s state (unit as printed)	as printed	wavelength	yes
verdet_constant_ratio	refractive	Verdet constant over its value at parameters.reference_wavelength_nm (the medium of the reference wavelength as the dataset’s)	1	wavelength	no	reference_wavelength_nm
rayleigh_cross_section	refractive	Rayleigh scattering cross section per particle (parameters.king_factor as used)	cm2	wavelength	no
rayleigh_cross_section_ratio	refractive	Rayleigh cross section of the gas over that of parameters.reference_material	1	wavelength	no	reference_material
refractivity_virial_coefficient	refractive	refractivity (or dielectric) virial coefficient of parameters.order (2 for B_R, the default; 3 for C_R; 4 for D_R); parameters.temperature_k	cm12/mol4, cm6/mol2, cm9/mol3	wavelength	no
unlike_pair_refractivity_virial_coefficient	refractive	the refractivity (or dielectric) virial coefficient B_st of the dataset’s material with parameters.partner, the first in sorted order (the cell inf is static); parameters.temperature_k, .contribution (induced, or total including orientation)	cm6/mol2	wavelength	no	contribution, partner, temperature_k
refractive_index	refractive	n, the real part of a solid’s complex index n + ik (parameters.axis for an anisotropic crystal; .temperature_k, .grade, .form where stated)	1	wavelength	no
permittivity_real	refractive	epsilon_1, the real part of a solid’s relative permittivity epsilon_1 + i epsilon_2 = (n + ik)^2 (parameters as for refractive_index)	1	wavelength	no
refractive_index_decrement	refractive	delta = 1 - n, the decrement of the real part of a solid’s complex index below 1, as x-ray tables print it (parameters as for refractive_index)	1	wavelength	no
refractive_index_deviation	refractive	a solid’s measured n minus the value of the formula parameters.reference (a formula id, source/formula) at the same wavelength	1	wavelength	no	reference
thermo_optic_coefficient	refractive	dn/dT of a solid (parameters.temperature_k)	1/K	wavelength	no
absorption_cross_section	absorption	total photoabsorption cross section per particle, below or above the ionisation threshold (parameters.temperature_k)	Mb, cm2	wavelength	no
photoionization_cross_section	absorption	photoionisation cross section per particle, above the ionisation threshold	Mb, cm2	wavelength	no
excited_state_photoionization_cross_section	absorption	one-photon photoionisation cross section of an excited level of the atom or molecule (parameters.initial_level: its configuration, term and J, or the source’s label), against the photon’s wavelength	Mb, cm2	wavelength	no	initial_level
photodissociation_quantum_yield	absorption	number of a stated product (or of a channel’s events) formed per photon absorbed, against the photon’s wavelength (parameters.product; .temperature_k where stated)	1	wavelength	no	product
transition_dipole_moment	absorption	electronic transition dipole moment between two states of the dataset’s species (parameters.states: the pair, the row label; .geometry: the nuclear geometry, e.g. a bond length, where the source gives more than one; .component: parallel or perpendicular to the axis, where stated)	D, au	label, none	no	states
two_photon_transition_strength	absorption	rotationally averaged two-photon transition strength delta^TP of the bound transition from the ground state to the labelled final level, in atomic units (parameters.polarization: linear_parallel or circular; .frequencies: degenerate, or the second photon’s energy; .rotational_average: the rotational average’s F, G and H as the source states them)	au	label	no	frequencies, polarization, rotational_average
two_photon_transition_amplitude	absorption	signed second-order amplitude of the bound two-photon transition from the ground state to a stated final level, both photons polarised along z and both orderings summed, against the first photon’s energy (the second’s is the level energy less it), as the source defines it (parameters.final_level; .gauge; .polarization; .definition: the source’s equation; .m_zz_per_unit: the zz element of the two-photon kernel M_zz, in atomic units, per unit of the printed amplitude; .method). Bound final levels only	1, au	label, wavelength	no	definition, final_level, gauge, m_zz_per_unit, method, polarization
two_photon_excitation_cross_section	absorption	frequency-integrated generalised cross section sigma_0^(2) of the two-photon excitation of a bound level from the ground state, W = sigma_0^(2) g Phi^2 with Phi the photon flux and g the line profile normalised to one (parameters.frequency_variable: angular or ordinary, the variable g is normalised in; .polarization; .photon_statistics: corrected, or the G2(0) of the measurement); a label names the final level, a wavelength is the exciting photon’s	cm4, m4	label, wavelength	no	frequency_variable, photon_statistics, polarization
integrated_cross_section	absorption	absorption cross section integrated from the abscissa to the x_upper column (unit as printed: cm2 nm, cm2 cm-1)	as printed	wavelength	no		x_upper
polarizability_imaginary	absorption	imaginary part of the polarizability above threshold	SI, angstrom3, au, cm3	wavelength	no
oscillator_strength	absorption	absorption oscillator strength of the transition at the abscissa, or of the labelled transition	1	label, wavelength	no
transition_probability	absorption	Einstein coefficient A_ki of spontaneous emission from the upper level k to the lower level i of the transition at the abscissa, or of the labelled transition (parameters.notation: the level notation of the labels, e.g. paschen or racah)	1/s	label, wavelength	no	notation
radiative_lifetime	absorption	radiative lifetime of the labelled level of the atom or molecule, the inverse of its total rate of spontaneous decay in the absence of collisions (parameters.method: how it was obtained, e.g. measured and extrapolated to zero pressure, semiempirical or calculated)	fs, ns, ps, s	label	no	method
level_polarizability	absorption	dipole polarizability of a stated level of the atom (parameters.configuration, .term, .j), at the abscissa’s wavelength or static (inf): the level shifts by -(1/2) alpha F^2 in a static field F and by -(1/4) alpha F^2 in an oscillating field of amplitude F (parameters.component: scalar, vector or tensor, with .definition the source’s shift formula for a vector or tensor part; .complex_part: real or imaginary; .method). Not the gas’s polarizability, which is polarizability	SI, angstrom3, au, cm3, kHz/(kV/cm)2	wavelength	no	complex_part, component, configuration, j, method, term
light_shift_coefficient	absorption	shift of the frequency of the multiphoton transition from the ground level to a stated final level per unit laser intensity, in the linear regime, positive to the blue, against the exciting photon’s wavelength (parameters.final_level; .photons; .intensity_definition: how the source defines the intensity; .polarization where stated)	Hz/(W/cm2)	wavelength	no	final_level, intensity_definition, photons
pressure_line_coefficient	absorption	collisional (pressure) broadening or shift of a bound line of the atom, per unit perturber pressure or number density, in the impact regime (parameters.effect: broadening, or shift, positive to the blue; .transition: the line in the source’s notation; .photons: 1 or 2; .frequency_scale: transition, the line’s own frequency, laser, the exciting photon’s, or not stated; .width: fwhm, hwhm, not stated, or none for a shift; .frequency_variable: ordinary or angular; .perturber: self or a gas; .temperature_k where stated). A two-photon line’s broadening is the decay of the ground-to-final coherence: its pure dephasing is what remains after the radiative and quenching parts	GHz/amagat, MHz/mbar, MHz/torr, cm-1/amagat, cm3/s	label, temperature	no	effect, frequency_scale, frequency_variable, perturber, photons, transition, width
collisional_quenching_rate_coefficient	absorption	rate coefficient of the collisional removal of the labelled excited level of the atom or molecule by a perturber, from 1/tau = 1/tau_rad + k2 [M] + k3 [M]^2 (parameters.perturber: a gas, or self; .order: 2, bimolecular, or 3, termolecular; .channel: total, or the product level of a state-to-state coefficient; .temperature_k where stated). A loss of population, not the pure dephasing of the level	cm3/s, cm6/s, m3/s, m6/s	label	no	channel, order, perturber
interval_oscillator_strength	absorption	oscillator strength integrated from the abscissa to the x_upper column	1	wavelength	no		x_upper
partial_cauchy_moment	absorption	S(parameters.order) of the oscillator strength from the abscissa to the x_upper column	au	wavelength	no	order	x_upper
differential_oscillator_strength	absorption	df/dE of the continuum at the photon energy	1/eV, 1/hartree, 1/rydberg	wavelength	no
extinction_coefficient	absorption	k, the imaginary part of a solid’s complex index n + ik (k > 0 absorbs; parameters as for refractive_index)	1	wavelength	no
permittivity_imaginary	absorption	epsilon_2, the imaginary part of a solid’s relative permittivity (epsilon_2 > 0 absorbs; parameters as for refractive_index)	1	wavelength	no
internal_transmittance	absorption	the fraction of the light entering a sample that reaches its far surface, reflection losses excluded, as a glass catalogue prints it (parameters.thickness_mm: the path length)	1	wavelength	no	thickness_mm
absorption_coefficient	absorption	attenuation coefficient of the intensity per length in a solid (parameters.base: e for I = I0 exp(-a z), 10 for I = I0 10^(-a z))	cm-1, m-1	wavelength	no	base
band_gap	absorption	band-gap energy of a solid (parameters.kind: optical, tauc, urbach, photoconductivity, exciton, mobility, effective (fitted to a model), assumed for a value a model takes as input, or not stated)	eV	label, none	no	kind
hyperpolarizability	third_order	second hyperpolarizability gamma per molecule (parameters.process, .convention, .part)	SI, au, esu	wavelength	no	convention, part, process
hyperpolarizability_ratio	third_order	gamma of the gas over gamma of parameters.reference_material (parameters.process, .part)	1	wavelength	no	part, process, reference_material
nonlinear_index	third_order	n2, n = n0 + n2 I, at the dataset’s state for a gas (parameters.part, .coefficient; for a solid also .pulse_fs, .technique, .polarization where stated)	cm2/W, m2/W	wavelength	yes	coefficient, part
nonlinear_index_field	third_order	n2 per squared field, n = n0 + n2 <E^2> (the esu n2 of the solid-state literature; parameters.definition: the source’s field average, e.g. ‘<E^2>’ of the real field, or the squared amplitude; .part, .coefficient)	esu, m2/V2	wavelength	no	coefficient, definition, part
nonlinear_index_ratio	third_order	n2 of the gas over n2 of parameters.reference_material at the same density (parameters.part)	1	wavelength	no	part, reference_material
nonlinear_susceptibility	third_order	third-order susceptibility chi(3), per volume at the dataset’s state or per unit density as printed (parameters.process, .convention, .part)	as printed	wavelength	no	convention, part, process
kerr_constant	third_order	dc Kerr constant at the dataset’s state, as printed (parameters.temperature_k)	as printed	wavelength	yes
molar_kerr_constant	third_order	the zero-density molar Kerr constant A_K (parameters.temperature_k; against temperature, parameters.wavelength_nm)	as printed	wavelength, temperature	no
kerr_virial_coefficient	third_order	Kerr virial coefficient, B_K (parameters.order 2, the default) or C_K (order 3) (parameters.temperature_k; against temperature, parameters.wavelength_nm)	as printed	wavelength, temperature	no
hyperpolarizability_density_coefficient	third_order	the density (pair) coefficient of chi(3) per molecule, chi(3)/N = gamma-term [1 + b N + …] (parameters.process, .part; parameters.pair for a mixture)	as printed	wavelength	no	part, process
two_photon_absorption_coefficient	third_order	two-photon absorption coefficient beta of a solid, dI/dz = -alpha I - beta I^2 (parameters.pulse_fs, .technique where stated)	cm/GW, cm/MW, cm/W, m/W	wavelength	no
multiphoton_absorption_coefficient	third_order	N-photon absorption coefficient of a solid, dI/dz = -beta_N I^N (parameters.photons; unit as printed)	as printed	wavelength	no	photons
critical_power	third_order	critical power for self-focusing (parameters.definition: the formula the source uses, or measured)	MW, W	wavelength	no	definition
polarizability_anisotropy	raman	polarizability anisotropy Delta alpha per molecule	SI, angstrom3, au, cm3	wavelength	no
polarizability_derivative	raman	derivative of the polarizability with respect to a normal coordinate (parameters.component: mean or anisotropy; .mode; .coordinate where it is not the mass-weighted normal coordinate: a bond length or a symmetry coordinate, as the source defines it; unit as printed)	as printed	wavelength	no	component, mode
depolarization_ratio	raman	depolarization ratio of scattered light (parameters.kind: rayleigh, raman, rotational_raman; .polarization: linear or natural)	1	wavelength	no	kind, polarization
raman_shift	raman	Raman shift or band origin of the labelled transition (parameters.transition when not per row)	cm-1	label, none	no
rotational_constant	raman	spectroscopic constant of the rotational ladder (parameters.constant: B, D, H, alpha_e, …; .vibrational_state_v)	GHz, MHz, cm-1	label, none	no	constant
vibrational_term_value	raman	vibrational energy G(v) of the level labelled by the row (the vibrational quantum number v), from parameters.reference: v0 (the ground level) or minimum (the potential minimum); .electronic_state	cm-1	label, none	no	reference
raman_scattering_activity	raman	Raman scattering activity of a normal mode, the invariant combination g (45 a’^2 + 7 g’^2) of the derivatives of the mean (a’) and anisotropic (g’) polarizability with respect to the mass-weighted normal coordinate, g the mode’s degeneracy (parameters.mode; unit as printed, e.g. angstrom4/amu)	as printed	label, none, wavelength	no	mode
raman_cross_section_ratio	raman	Raman scattering cross section of a transition relative to that of parameters.reference_material’s reference transition (.reference_transition, usually the N2 Q branch) at the same excitation (parameters.transition; .geometry: how the scattering was observed)	1	label, none, wavelength	no	reference_material, transition
raman_cross_section	raman	differential Raman scattering cross section of a transition (parameters.transition; unit as printed, e.g. cm2/sr)	as printed	wavelength	no	transition
raman_linewidth	raman	linewidth of a Raman transition, or its pressure-broadening coefficient (parameters.transition, .width: hwhm, fwhm or not stated; .perturber for a coefficient: self, a gas id or air; .term for one term of a width law, e.g. the Dicke coefficient A of A/rho; .temperature_k where stated; unit as printed)	as printed	density, label, none, pressure, temperature	no	transition, width
raman_line_shift	raman	pressure (collisional) shift of a Raman line, or its coefficient (parameters.transition, .perturber, .temperature_k where stated; unit as printed)	as printed	density, label, none, pressure, temperature	no	perturber, transition
broadening_temperature_exponent	raman	exponent N of a broadening coefficient’s temperature law gamma(T) = gamma(T0) (T0 / T)^N (parameters.transition, .perturber, .reference_temperature_k)	1	label, none	no	perturber, transition
raman_transition_polarizability	raman	matrix element of a polarizability invariant between the two states of a Raman transition, alpha_if (parameters.transition, .invariant: mean or anisotropy, or the component parallel or perpendicular to the molecular axis)	SI, angstrom3, au, cm3	label, none, wavelength	no	invariant, transition
raman_gain	raman	steady-state stimulated Raman gain coefficient of a transition at the dataset’s state (parameters.transition, .pump_nm when not the abscissa; unit as printed, e.g. cm/GW)	as printed	density, label, none, pressure, wavelength	yes	transition
dephasing_time	raman	coherence (T2) time of a Raman transition (parameters.transition; unit as printed)	as printed	density, label, none, pressure, temperature	no	transition
raman_fraction	raman	fraction f_R of the delayed (Raman) response in a solid’s nonlinear response (parameters.definition: how the source defines it)	1	label, none	no	definition
raman_mode	raman	one mode of a multi-mode Raman response of a solid: its amplitude, with the columns shift (cm-1) and the gaussian_width and lorentzian_width (as printed, parameters.width: fwhm or hwhm)	as printed	label, none	no	width	gaussian_width, lorentzian_width, shift
raman_response_time	raman	a time constant of a model Raman response (parameters.constant: tau1, tau2, …; .model)	fs, ns, ps, s	label, none	no	constant, model
ionization_energy	ionisation	ionisation energy (parameters.kind: adiabatic or vertical; .final_state)	cm-1, eV, hartree	label, none	no	kind
level_energy	ionisation	energy of a level of an atom or ion above its ground level (parameters.configuration, .term, .j)	cm-1, eV	label, none	no	configuration, j, term
electronic_state_energy	ionisation	energy of an excited electronic state of a molecule above its ground state (parameters.state; .kind: Te, the potential minimum, T0, the lowest vibrational level, or onset, the long-wavelength onset of a band; .one_photon and .two_photon from the ground state: allowed, forbidden or spin_forbidden, where stated)	cm-1, eV	label, none	no	kind, state
appearance_energy	ionisation	appearance energy of a fragment ion (parameters.fragment)	cm-1, eV	label, none	no	fragment
dissociation_energy	ionisation	energy of a dissociation limit of the dataset’s species (neutral or ion) into the stated products (parameters.products, with their states where stated; .kind: D0 from the lowest level, De from the potential minimum, or threshold: the limit measured from the ground state of parameters.reference_state, e.g. the neutral molecule for a dication’s limit)	cm-1, eV, hartree, kJ/mol	label, none	no	kind, products
ionic_state_population	ionisation	population of an electronic state of the molecular ion that a pulse leaves, as a fraction of the ions or of the molecules (parameters.state; .normalisation: ions or molecules; .wavelength_nm, .pulse_fs, .polarization: the pulse; .intensity_w_cm2 where one number; .method: measured, or the calculation), against peak intensity or as one number	1	intensity, label, none	no	normalisation, polarization, pulse_fs, state, wavelength_nm
fragmentation_branching_ratio	ionisation	yield of one fragmentation channel of the dataset’s species over that of a reference (parameters.channel: the products; .reference: the parent ion, all ions, all channels, or another channel; .excitation: photoionisation at the abscissa’s photon energy, or a strong-field pulse with .wavelength_nm, .pulse_fs, .polarization; .detection_correction: how the detector’s efficiency was treated), against intensity, the photon’s wavelength or energy, or as one number	1	intensity, label, none, wavelength	no	channel, detection_correction, excitation, reference
kinetic_energy_release	ionisation	total kinetic energy the fragments of a channel carry away (parameters.channel; .kind: peak, mean, asymptotic or calculated; .state: the parent state where assigned; the pulse where measured)	eV	label, none	no	channel, kind
dissociation_time	ionisation	time constant of a dissociation of the dataset’s species (parameters.channel; .kind: lifetime of the dissociating state, appearance time of a fragment, or calculated; a collisional time states its .pressure and partner)	fs, ns, ps, s	label, none, pressure	no	channel, kind
dissociative_recombination_rate_coefficient	ionisation	rate coefficient of the dissociative recombination of the dataset’s molecular ion with an electron, k in dn_e/dt = -k n_e n_ion (parameters.products, or all channels; .law: value, the coefficient at the abscissa’s electron temperature, or power_law, the value at .reference_temperature_k scaled by (T_ref/T_e)^.exponent; .temperature_range_k where stated)	cm3/s, m3/s	label, none, temperature	no	law, products
ionization_rate	ionisation	field-ionisation rate against intensity or field (parameters.wavelength_nm, inf for a static field; .polarization: linear, circular or static; unit as printed)	as printed	field, intensity	no	polarization, wavelength_nm
ionization_yield	ionisation	ion yield or probability against intensity (parameters.wavelength_nm, .pulse_fs, .polarization; .pulse_envelope and .cep where stated; unit as printed)	as printed	intensity	no	polarization, pulse_fs, wavelength_nm
ground_state_survival	ionisation	probability that a pulse leaves the atom in its initial (ground) state, against the peak intensity, read at a stated time; its complement counts excitation as well as ionisation (parameters.wavelength_nm, .pulse_fs, .polarization, .read_at: when the population is read; .pulse_envelope and .cep where stated)	1	intensity	no	polarization, pulse_fs, read_at, wavelength_nm
ionization_yield_spectrum	ionisation	ion yield or probability against the photon energy or wavelength at a fixed peak intensity (parameters.intensity_w_cm2, .pulse_cycles: the pulse’s length in optical cycles, which fixes its duration at each wavelength, .polarization; .pulse_envelope and .cep where stated; unit as printed)	as printed	wavelength	no	intensity_w_cm2, polarization, pulse_cycles
ionization_yield_ratio	ionisation	ratio of the material’s ionisation yield, as the source defines it (singly charged ions, or all channels, or electrons), to a companion species’ measured with it, against intensity, wavelength or as one number (parameters.companion; .wavelength_nm, .pulse_fs, .polarization where one value; .detection_correction: how the ion detector’s efficiency was treated, e.g. none, Z/sqrt(M), optical)	1	intensity, label, wavelength	no	companion, detection_correction, polarization
ionization_phase_shift	ionisation	phase shift of a probe beam from the electrons a pump pulse leaves, averaged over the probe’s profile and normalised to a gas pressure, against the pump’s peak intensity (parameters.wavelength_nm, .pulse_fs, .polarization: the pump; .probe_wavelength_nm; .pressure_atm: the pressure normalised to; the beams’ sizes where stated)	rad	intensity	no	polarization, pressure_atm, probe_wavelength_nm, pulse_fs, wavelength_nm
tunnelling_structure_coefficient	ionisation	asymptotic coefficient of the ionising orbital in a tunnelling theory, one per partial wave l, the row label (parameters.model: moadk, adk or wfat; .orbital; .m; .normalisation: how the coefficient is defined)	1	label, none	no	m, model, normalisation, orbital
ionization_model_parameter	ionisation	a constant fitted within a named ionisation-rate model, not a property of the material alone (parameters.model, .parameter: its symbol; unit as printed)	as printed	label, none	no	model, parameter
saturation_intensity	ionisation	peak intensity at which a pulse saturates the ionisation of an atom, as the source defines it (parameters.definition; .photons, .pulse_fs, .pulse_shape: the pulse)	W/cm2, W/m2	wavelength	no	definition, pulse_fs
multiphoton_ionization_cross_section	ionisation	generalised N-photon ionisation cross section (parameters.photons; unit as printed, cm^2N s^(N-1))	as printed	wavelength	no	photons
multiphoton_ionization_polarization_ratio	ionisation	ratio of the generalised N-photon ionisation cross section for circular polarisation to that for linear (parameters.photons)	1	wavelength	no	photons
effective_mass	ionisation	effective mass of a solid’s carriers, in electron masses (parameters.carrier: electron, hole, reduced or not stated)	m_e	label, none	no	carrier
electron_collision_time	ionisation	momentum-relaxation (collision) time of a solid’s conduction electrons in a Drude model	fs, ns, ps, s	label, none	no
electron_trapping_time	ionisation	decay (trapping or recombination) time of the conduction-electron density	fs, ns, ps, s	label, none	no
avalanche_coefficient	ionisation	impact-ionisation (avalanche) coefficient of a solid (unit as printed: cm2/J, 1/s, …; parameters.definition)	as printed	label, none, wavelength	no	definition
atom_density	ionisation	density of the particles available for ionisation in a solid (parameters.counts: molecules, atoms or valence_electrons)	cm-3, m-3	label, none	no	counts
damage_threshold_fluence	damage	laser-induced damage or breakdown threshold fluence (parameters.site: bulk or surface; .criterion; .shots; the pulse length as the abscissa (duration, with .wavelength_nm) or as .pulse_fs)	J/cm2, J/m2	duration, wavelength	no	site
damage_threshold_intensity	damage	laser-induced damage or breakdown threshold intensity (parameters as for damage_threshold_fluence)	W/cm2, W/m2	duration, wavelength	no	site
damage_threshold_energy	damage	pulse energy at the damage or breakdown threshold for a stated focusing (parameters as for damage_threshold_fluence, and .numerical_aperture)	J, nJ, uJ	duration, wavelength	no	site
mole_fraction	composition	amount-of-substance fraction of the material (a gas) in a mixture (parameters.mixture: the mixture, as the source defines it, such as ‘dry air’)	1, mol/mol, ppm	none	no	mixture
dilute_viscosity	transport	the shear viscosity of the gas in the limit of zero density, a function of temperature alone	Pa s	temperature	no
ideal_gas_heat_capacity	transport	the molar isobaric heat capacity of the ideal gas, c_p0(T)	J/(mol K)	temperature	no
second_virial_coefficient	thermodynamic	the second (pressure, density) virial coefficient B(T) of the pure gas, Z = 1 + B rho + …	cm3/mol	temperature	no
cross_second_virial_coefficient	thermodynamic	the unlike-pair second virial coefficient B_12(T) of the dataset’s material with parameters.partner, B_mix = sum_st x_s x_t B_st	cm3/mol	temperature	no	partner
excess_second_virial_coefficient	thermodynamic	the excess second virial coefficient E = B_12 - (B_11 + B_22)/2 of the dataset’s material with parameters.partner	cm3/mol	temperature	no	partner
mixture_second_virial_coefficient	thermodynamic	the second virial coefficient B_mix(T) of a binary mixture of the dataset’s material, at mole fraction parameters.mole_fraction, with parameters.partner	cm3/mol	temperature	no	mole_fraction, partner
mixture_compressibility_factor	thermodynamic	Z = p / (rho R T) of a binary mixture of the dataset’s material, at mole fraction parameters.mole_fraction, with parameters.partner; parameters.temperature_k	1	density, pressure	no	mole_fraction, partner, temperature_k
mixture_density	thermodynamic	the molar (or mass) density of a binary mixture of the dataset’s material, at mole fraction parameters.mole_fraction, with parameters.partner; parameters.temperature_k	g/cm3, kg/m3, mol/L, mol/cm3, mol/m3	pressure	no	mole_fraction, partner, temperature_k

The first four refractive quantities each determine the polarizability at their frequency (optmat.gas.reduction.polarizability()). The others constrain the dispersion indirectly; the fits give them forward models. A polarizability_correction (a zero-point or pure vibrational correction) is never read as a total.

The abscissae and their units:

Abscissa	Units	Cells
wavelength	m, nm, um, angstrom, cm-1, um-1, eV, hartree, rydberg	numbers; inf for the static limit; not stated
order	1	the order of a moment
temperature	K, C	numbers
pressure	Pa, kPa, MPa, bar, atm, torr, psia (lbf/in^2)	numbers
density	m-3, cm-3, amagat, mol/m3, mol/cm3, mol/L	numbers
intensity	W/m2, W/cm2	numbers
duration	s, ns, ps, fs	numbers (a pulse length)
field	V/m, V/cm, au	numbers (a static or peak field; au is E_h / (e a0))
label	none	names of the rows (a transition, a state)
none	none	empty: the value stands alone, described by its parameters

Dataset.vacuum_wavelength() converts a wavelength abscissa, Dataset.abscissa_values() any numeric one to SI, and Dataset.column_values(name) an extra column.

Third-order quantities

The third-order values keep the source’s own quantity, convention and conditions; nothing is converted on entry. Each states:

• process:

  • static;

  • kerr, the intensity-dependent index gamma(-w; w, w, -w);

  • eshg, gamma(-2w; w, w, 0);

  • dc_kerr, gamma(-w; w, 0, 0);

  • thg, gamma(-3w; w, w, w);

  • cars, gamma(-w_as; w_p, w_p, -w_s);

  • other. The abscissa is the fundamental (input) wavelength, or the pump for cars, with the Stokes wavelength in parameters or notes.

• convention: one of the named definitions of optmat.vocabulary.CONVENTIONS:

  • T, the Taylor-series (Buckingham-Orr) convention of Shelton & Rice (p = … + gamma E^3/6);

  • ward_1969 (Ward’s per-molecule chi in esu);

  • lehmeier_1985 (P = 4 eps0 chi E E E);

  • chi_cars_per_amagat;

  • rosasco_1985_hellwarth;

  • hellwarth_sigma;

  • maker_terhune_c;

  • bjorklund_1975.

  A new definition is added there, with its relation to gamma_T where known.

• part: electronic, vibrational, rotational, vibrational_rotational (Shelton’s gamma^vR), electronic_vibrational, total, instantaneous (a pulse-dependent mixture, as Nibbering’s), or unknown.

• coefficient (for n2): self (n = n0 + n2 I of one beam) or probe (the index a weak probe sees, which is twice the self coefficient for the same polarization).

• Measurement conditions: the pulse duration and the probe wavelength go in parameters (pulse_fs, probe_nm) where the value depends on them.

A published dispersion fit, such as gamma = gamma0 [1 + A nu_L^2 + B nu_L^4] with nu_L^2 the sum of the squares of the four wavenumbers, is a [[formulas]] entry without a form. Its coefficients are strings as printed, and its variable and fitted process are stated.