optmat.gas.raman_response#

The Raman response function of a molecular gas or a gas mixture (TC-685 to TC-690).

A molecule’s delayed third-order response is a sum of damped oscillators, one per Raman line (optmat.gas.raman). This module assembles them into the response function itself, with its polarisation (tensor) structure and its dependence on the density, so that a propagation code only samples it.

The convention (TC-442, TC-685). For a field linearly polarised along \(x\), the Raman polarisation of a gas of number density \(N\) is

\[P_x(t) = \varepsilon_0 N E_x(t) \int_0^\infty h(\tau) E_x^2(t - \tau)\, d\tau, \qquad h(\tau) = \sum_k A_k \sin(\Omega_k \tau)\, e^{-\Gamma_k \tau},\]

with \(A_k\) in m^5 V^-2 s^-1 per molecule of the gas (of the mixture: a constituent’s lines carry its mole fraction), \(\Omega_k\) in rad/s and \(\Gamma_k = \pi \Delta\nu_k\), \(\Delta\nu_k\) the line’s full width at half maximum in Hz. Its transform, with the sign convention of optmat.gas.raman.stokes_gain(), is

\[H(\omega) = \int_0^\infty h(\tau) e^{i\omega\tau} d\tau = \sum_k \frac{A_k \Omega_k} {\Omega_k^2 + \Gamma_k^2 - \omega^2 - 2 i \Gamma_k \omega},\]

so that \(H(\Omega_k) \approx i A_k / (2\Gamma_k)\) at a resonance and \(H(0) = \int h\, d\tau\).

The tensor form (Hellwarth). For any polarisation,

\[P_i(t) = \varepsilon_0 N \int_0^\infty R_{ijkl}(\tau)\, E_j(t) E_k(t - \tau) E_l(t - \tau)\, d\tau, \qquad R_{ijkl} = a(\tau)\, \delta_{ij}\delta_{kl} + \tfrac{1}{2} b(\tau) (\delta_{ik}\delta_{jl} + \delta_{il}\delta_{jk}),\]

and \(h = a + b\) for a single linear polarisation. Each line has an isotropic (rank-0) share, from the mean polarizability \(\bar\alpha\), and an anisotropic (rank-2) share, from its anisotropy. The isotropic share enters \(a\) only; the anisotropic share \(h_2\) has \(a = -h_2/2\), \(b = 3h_2/2\) (the induced change of the anisotropic polarizability is the traceless part of \(E E\)). A weak probe polarised across the pump sees \(a\): the rotational lines give it \(-1/2\) of the parallel response, the isotropic vibrational lines all of it.

The rotational S lines are anisotropic (\(\Delta\alpha\)).
A vibrational Q(J) line has both shares. Its anisotropic share is \((4/45)\, b_{J,J}\, \gamma'^2 P_J / (\hbar\varepsilon_0)\), with the Placzek-Teller coefficient \(b_{J,J} = J(J+1)/[(2J-1)(2J+3)]\) and \(\gamma'\) the transition anisotropy: from its components where they are curated (H2, D2), else from the Q branch’s depolarization ratio \(\rho = 3 b\gamma'^2 / (45\bar\alpha'^2 + 4 b\gamma'^2)\) (TC-686).
The vibrational O and S branches (\(\Delta J = \mp 2\) with \(v = 0 \to 1\)), anisotropic only, are left out: they carry \(3\times\) the anisotropic Q share, 8 % of the Q branch for N2, 19 % for O2 and 3 % for H2 and D2, spread over some 100 cm^-1 about the band (TC-686).

The widths and the density. Every curated width law has the form \(\Delta\nu = c + d/n + \beta n\) at a fixed temperature and composition (n in amagat; optmat.gas.linewidths), so the response keeps the three coefficients of each line (TC-687). A line’s frequency shifts with the density where a shift is curated (H2’s Q branch; TC-688). The amplitudes depend on the temperature and the pump wavelength only. The response is therefore fixed by (temperature, composition, wavelength), and GasRamanResponse.decay_rates() and GasRamanResponse.frequencies() give its density dependence cheaply, for any array of densities: the part a propagation code evaluates along a density gradient. Lines whose widths follow one law have the same damping_group: they can be summed into one damped kernel without approximation.

Ranges (ModelRangeWarning, TC-688). The lines are independent Lorentzians with collisional (impact) widths, which holds between two densities, found for the strongest line of each band:

below, the motion of the molecules sets the width. For a line with a Dicke term the diffusion law holds above Herring et al.’s cutoff \(\rho_c = 3.33\, d / \Delta\nu_D\) (their Eq. (3)), with \(\Delta\nu_D\) the Doppler width for forward scattering (their Eq. (4)); below it \(d/n\) is capped at \(\Delta\nu_D\), a Lorentzian stand-in for the Doppler limit. For a line without one, the limit is the density at which its collisional width falls to \(\Delta\nu_D\);
above, the line’s width reaches the spacing to its nearest neighbour: the overlap and mixing of the lines (the collisional narrowing of a Q branch) is not modelled (TC-527);
the temperatures of each band’s width measurements (warned when the response is built).

What is not here. The sampling of the response on a time grid, its taper and padding, and any grouping or low-rank tabulation for speed belong to the propagation code (the manual page The Raman response). The response is a coherent (Kubo) response: the redistribution of the M sublevels within a level, which a slow isothermal measurement also sees, is not part of it (TC-493).

References#

R. W. Hellwarth, “Third-order optical susceptibilities of liquids and solids”, Prog. Quantum Electron. 5, 1 (1977).
G. Placzek and E. Teller, “Die Rotationsstruktur der Ramanbanden mehratomiger Moleküle”, Z. Phys. 81, 209 (1933).
1. 1. Long, The Raman Effect (Wiley, 2002), chapters 5 and 6.

Module Attributes

`EVALUATION_VERSION`	The version of this module's evaluation code, in the identity of every model that evaluates through it; raised whenever the code changes its output (OEP 1, section 4.8).
`RAMAN_RESPONSE_FILE`	The range, shift and mixture choices of the responses, each with its reason.
`Component`	A part of the response.

Functions

`placzek_teller_q`(j)	Return the Placzek-Teller coefficient of the Q lines, \(b_{J,J}\).
`raman_response`(gas, temperature, *[, ...])	Return the Raman response of a gas or a mixture at a temperature.
`raman_response_status`(gas)	Return the status a gas's Raman response would have, without building it.

Classes

`GasRamanResponse`(composition, temperature, ...)	The Raman response of a gas or a mixture at one temperature and composition.
`RamanGroup`(index, lines, line_ids, ...)	One damping group of a Raman response: lines that share a width law and shift.

optmat.gas.raman_response.Component#

A part of the response.

parallel: \(h = a + b\), the response to a single linear polarisation. isotropic and anisotropic: the rank-0 and rank-2 shares of parallel. a and b: Hellwarth’s two functions; a is the response a weak probe polarised across the pump sees.

alias of Literal[‘parallel’, ‘isotropic’, ‘anisotropic’, ‘a’, ‘b’]

optmat.gas.raman_response.EVALUATION_VERSION: Final = 1#: The version of this module’s evaluation code, in the identity of every model that evaluates through it; raised whenever the code changes its output (OEP 1, section 4.8).

class optmat.gas.raman_response.GasRamanResponse(composition, temperature, wavelength, species, band, branch, j, frequency, isotropic, anisotropic, width_constant, width_dicke, width_broadening, doppler_width, shift, damping_group, density_range, temperature_range, sources=<factory>, reasons=<factory>, *, status='user', status_reason='', modified=(), base='', material='', population_floor=nan)[source]#

Bases: Identified

The Raman response of a gas or a mixture at one temperature and composition.

Built by raman_response(), or by from_lines() from a caller’s lines. Every array has one entry per line (a term of the response); the lines are grouped by species and band, the rotational S lines first. The damping groups and the density range are derived from the lines by one rule (from_lines()).

Its overrides (with_parameters()) act on the assembled lines: amplitude_scale, a factor on every amplitude; width_scale, a factor on c, d, beta and the Doppler cap alike, which keeps the groups; and width_law, {band: (c, d, beta, cap)} for every line of a band ("rotation", a mode, or "<species> <band>" in a mixture). A different temperature, composition, pump wavelength or population floor is a new raman_response(), not an override.

Attributes:

compositiontuple of tuple of (str, float): The species and their mole fractions (a pure gas is one species at 1).
temperaturefloat: Temperature, K.
wavelengthfloat or None: The pump wavelength at which the vibrational strengths are dispersed, m; None for the strengths as curated.
speciestuple of str: The species of each line.
bandtuple of str: The band of each line (rotation or the vibrational mode).
branchtuple of str: S or Q.
jnumpy.ndarray: The lower rotational level (-1 for an unresolved band).
frequencynumpy.ndarray: \(\Omega\) at zero density, rad/s.
isotropic, anisotropicnumpy.ndarray: The rank-0 and rank-2 shares of each line’s amplitude for a single linear polarisation, per molecule of the gas, m^5 V^-2 s^-1.
width_constantnumpy.ndarray: The density-independent width \(c\), Hz.
width_dickenumpy.ndarray: The Dicke coefficient \(d\), Hz amagat.
width_broadeningnumpy.ndarray: The broadening coefficient \(\beta\), Hz/amagat.
doppler_widthnumpy.ndarray: The forward-scattering Doppler width that caps a Dicke term, Hz (0 where the line has no Dicke term).
shiftnumpy.ndarray: The line’s frequency shift per unit density, Hz/amagat.
damping_groupnumpy.ndarray: Lines with the same number share their width and shift at every density.
density_rangetuple of float: The number densities between which the lines are independent collisional Lorentzians (module docstring), m^-3.
temperature_rangetuple of float: The temperatures covered by the width measurements of every band, K.
sourcesdict of str to str: The datasets and formulas behind the response, by what they give.
reasonsdict of str to str: Why each choice was made.
materialstr: What the response is of: a species, a named mixture ("dry air") or, for mole fractions given directly, the species joined by +.
population_floorfloat: The relative population below which rotational levels were left out.
statusstr: validated, or provisional where a constituent’s widths are a stopgap (CO2 and N2O, TC-542); user for a response a caller built.

DERIVED: ClassVar[tuple[str, ...]] = ('damping_group', 'density_range')#: Fields derived from the inputs, which an override may not name.

EVALUATES_THROUGH: ClassVar[tuple[str, ...]] = ('optmat.gas.raman_response',)#

EVALUATION_VERSION: ClassVar[int] = 1#

IDENTITY_KIND: ClassVar[str] = 'raman_response'#

INPUTS: ClassVar[tuple[str, ...]] = ('amplitude_scale', 'width_law', 'width_scale')#: The parameters with_parameters() may change.

property amplitude: Float[ndarray, 'n']#

The amplitude of each line for a single linear polarisation, m^5 V^-2 s^-1.

Returns:

numpy.ndarray: isotropic + anisotropic.

anisotropic: Float[ndarray, 'n']#

band: tuple[str, ...]#

branch: tuple[str, ...]#

check_densities(density)[source]#

Warn once for the densities a consumer will evaluate the groups at.

The group view (groups()) does not warn; a propagation code declares its densities here instead.

Parameters:

densityarray_like: Number densities, m^-3, >= 0.

Raises:

DataError: If a density is negative or not finite.

Warns:

ModelRangeWarning: If any is outside density_range.

component_amplitudes(component='parallel')[source]#

Return each line’s amplitude in one part of the response.

Parameters:

component{“parallel”, “isotropic”, “anisotropic”, “a”, “b”}, optional: The part (Component).

Returns:

numpy.ndarray: The amplitudes, m^5 V^-2 s^-1.

Raises:

DataError: If the component is not one of these.

composition: tuple[tuple[str, float], ...]#

damping_group: Int[ndarray, 'n']#

decay_rates(density)[source]#

Return every line’s dephasing rate \(\Gamma = \pi \Delta\nu\).

Parameters:

densityarray_like: Total number densities, m^-3, > 0.

Returns:

numpy.ndarray: \(\Gamma\), 1/s, shape (len(self),) + shape(density).

Warns:

ModelRangeWarning: As fwhm().

Examples

>>> from optmat.gas.linewidths import AMAGAT
>>> response = raman_response("H2", 295.0, wavelength=800e-9)
>>> rates = response.decay_rates(np.array([2.0, 10.0]) * AMAGAT)
>>> rates.shape == (len(response), 2)
True

density_range: tuple[float, float]#

doppler_width: Float[ndarray, 'n']#

frequencies(density)[source]#

Return every line’s angular frequency \(\Omega\) at number densities.

Parameters:

densityarray_like: Total number densities, m^-3, > 0.

Returns:

numpy.ndarray: \(\Omega\), rad/s, shape (len(self),) + shape(density).

Warns:

ModelRangeWarning: As fwhm().

frequency: Float[ndarray, 'n']#

classmethod from_lines(species, temperature, frequency, isotropic, anisotropic, width_constant, width_dicke, width_broadening, doppler_width, shift, *, band=None, branch=None, j=None, mass=None, composition=None, wavelength=None, temperature_range=None, citation='', material='', population_floor=nan, sources=None, reasons=None)[source]#

Return a Raman response from its lines, as raman_response() does.

The damping groups number the lines by first appearance of their species, band and width law (c, d, beta, cap, shift). The density range is each band’s (TC-688) for its strongest line, with that line’s forward-scattering Doppler width (Herring et al.’s Eq. 4, from the species’ mass): the narrowest over the bands.

Parameters:

speciesstr or sequence of str

The species of every line, or of each.

temperaturefloat

frequencyarray_like

Each line’s frequency at zero density, rad/s.

isotropic, anisotropicarray_like

The two shares of each line’s amplitude, m^5 V^-2 s^-1.

width_constant, width_dicke, width_broadeningarray_like

c (Hz), d (Hz amagat) and beta (Hz/amagat).

doppler_widtharray_like

The Doppler cap of each line’s Dicke term, Hz; 0 without one.

shiftarray_like

The frequency shift per unit density, Hz/amagat.

band, branchsequence of str or None, optional

Each line’s band ("rotation" by default) and branch ("S").

jarray_like or None, optional

Each line’s lower level; -1 (unresolved) by default.

massfloat or Mapping or None, optional

The molecular mass in u, one or by species; the curated one of a curated species by default.

compositionMapping or None, optional

Species to mole fraction; each species at its share of the lines’ by default (one species: 1).

wavelengthfloat or None, optional

The pump wavelength the strengths are dispersed at, m.

temperature_rangetuple of float or None, optional

The temperatures the widths hold over, K; the temperature by default.

citationstr, optional

Where the lines come from.

materialstr, optional

What the response is of; the species joined by + by default.

population_floorfloat, optional

The population below which levels were left out, if one was.

sources, reasonsMapping or None, optional

The response’s sources and reasons.

Returns:

GasRamanResponse: The response, status user.

Raises:

ValueError: If the arrays differ in length, a Dicke term has no cap, or a species’ mass is unknown.

Examples

>>> response = GasRamanResponse.from_lines(
...     "X2", 295.0, [1e13], [0.0], [1e-40], [1e9], [0.0], [1e8], [0.0], [0.0],
...     mass=30.0)
>>> response.identity.material, int(response.damping_group[0])
('X2', 0)

fwhm(density)[source]#

Return every line’s full width at half maximum at number densities.

Parameters:

densityarray_like: Total number densities, m^-3, > 0.

Returns:

numpy.ndarray: FWHM, Hz, shape (len(self),) + shape(density).

Warns:

ModelRangeWarning: Outside density_range.

groups()[source]#

Return the damping groups, with their laws in SI (OEP 1, section 6.7).

Returns:

tuple of RamanGroup: In the order of damping_group; their responses sum to response().

Examples

>>> h2 = raman_response("H2", 295.0)
>>> [g.line_ids[0] for g in h2.groups() if g.shifted][:1]
['H2/v1/Q/0']

isotropic: Float[ndarray, 'n']#

j: Int[ndarray, 'n']#

property line_id: tuple[str, ...]#

A stable identifier of each line: species/band/branch/J.

J is the lower level, or - for an unresolved band ("N2/rotation/S/6", "H2/v1/Q/1").

Returns:

tuple of str: One per line.

lines(density)[source]#

Return the lines at a number density, for optmat.gas.raman’s formulas.

Parameters:

densityfloat: Total number density, m^-3, > 0.

Returns:

RamanLines: Frequencies, amplitudes (parallel) and widths at that density.

Warns:

ModelRangeWarning: As fwhm().

material: str = ''#

population_floor: float = nan#

reasons: Mapping[str, str]#

property references: tuple[str, ...]#

The curated sources the response rests on.

Returns:

tuple of str: Source ids, sorted.

response(time, density, component='parallel')[source]#

Return the response function \(h(\tau)\) at a number density.

Parameters:

timearray_like: Delay after the impulse, s (the response is zero before it).
densityfloat: Total number density, m^-3, > 0.
component{“parallel”, “isotropic”, “anisotropic”, “a”, “b”}, optional: The part of the response (Component).

Returns:

numpy.ndarray: \(h\), m^5 V^-2 s^-1, with the shape of time.

Warns:

ModelRangeWarning: As fwhm().

Examples

Nitrogen’s response first peaks 75 fs after the impulse, as the molecules begin to align:

>>> from optmat.gas.linewidths import AMAGAT
>>> response = raman_response("N2", 295.0)
>>> t = np.linspace(0.0, 0.2e-12, 2001)
>>> f"{t[np.argmax(response.response(t, AMAGAT))] * 1e15:.0f}"
'75'

rotational_nonlinear_index(density)[source]#

Return the rotational nonlinear index for a long pulse.

optmat.gas.raman.rotational_nonlinear_index() of lines().

Parameters:

densityfloat: Total number density, m^-3, > 0.

Returns:

float: n2, m^2/W.

Warns:

ModelRangeWarning: As fwhm().

shift: Float[ndarray, 'n']#

sources: Mapping[str, str]#

species: tuple[str, ...]#

spectrum(omega, density, component='parallel')[source]#

Return \(H(\omega) = \int_0^\infty h(\tau) e^{i\omega\tau} d\tau\).

Parameters:

omegaarray_like: Angular frequency, rad/s.
densityfloat: Total number density, m^-3, > 0.
component{“parallel”, “isotropic”, “anisotropic”, “a”, “b”}, optional: The part of the response (Component).

Returns:

numpy.ndarray: \(H\), m^5 V^-2, complex, with the shape of omega. Its imaginary part is positive at a Stokes resonance (gain).

Warns:

ModelRangeWarning: As fwhm().

stokes_gain(pump_wavelength, density)[source]#

Return each line’s steady-state Stokes gain, pump and Stokes polarised alike.

optmat.gas.raman.stokes_gain() of lines().

Parameters:

pump_wavelengthfloat: Vacuum wavelength of the pump, m.
densityfloat: Total number density, m^-3, > 0.

Returns:

numpy.ndarray: The gain of each line, m/W.

Warns:

ModelRangeWarning: As fwhm().

temperature: float#

temperature_range: tuple[float, float]#

wavelength: float | None#

width_broadening: Float[ndarray, 'n']#

width_constant: Float[ndarray, 'n']#

width_dicke: Float[ndarray, 'n']#

optmat.gas.raman_response.RAMAN_RESPONSE_FILE: Final = PosixPath('/home/docs/checkouts/optmat/checkouts/7/src/optmat/data/gas/raman_response.toml')#: The range, shift and mixture choices of the responses, each with its reason.

class optmat.gas.raman_response.RamanGroup(index, lines, line_ids, gamma_constant, gamma_dicke, gamma_doppler, gamma_broadening, shift, frequency, isotropic, anisotropic)[source]#

Bases: object

One damping group of a Raman response: lines that share a width law and shift.

The group’s decay rate at a total number density \(N\) (m^-3) is \(\Gamma_g(N) = \gamma_c + \min(\gamma_d/N,\ \gamma_D) + \gamma_\beta N\), 1/s, and every line’s angular frequency \(\omega_k + \sigma_g N\), so that the group’s response is \(e^{-\Gamma_g t}\sum_k A_k \sin((\omega_k + \sigma_g N) t)\) (OEP 1, section 4.5). Where \(\sigma_g = 0\) the row of amplitudes and frequencies is fixed and only the decay depends on the density.

Attributes:

indexint: The group’s number (damping_group).
linestuple of int: The indices of its lines in the response.
line_idstuple of str: Their identifiers (GasRamanResponse.line_id).
gamma_constantfloat: \(\gamma_c = \pi c\), 1/s.
gamma_dickefloat: \(\gamma_d = \pi d N_\text{amg}\), 1/s m^-3; 0 without a Dicke term.
gamma_dopplerfloat: \(\gamma_D = \pi \Delta\nu_D\), the Dicke term’s cap, 1/s; 0 without one.
gamma_broadeningfloat: \(\gamma_\beta = \pi \beta / N_\text{amg}\), 1/s m^3.
shiftfloat: \(\sigma_g = 2\pi s_g / N_\text{amg}\), rad s^-1 m^3.
frequencynumpy.ndarray: The lines’ angular frequencies at zero density, rad/s.
isotropic, anisotropicnumpy.ndarray: Their amplitudes’ two shares, m^5 V^-2 s^-1.

anisotropic: Float[ndarray, 'm']#

decay_rate(density)[source]#

Return the group’s decay rate, down to zero density.

At N = 0 it is the law’s limit: the capped Dicke term tends to its cap. It does not warn outside the response’s validated range; see GasRamanResponse.check_densities().

Parameters:

densityarray_like: Total number densities, m^-3, >= 0.

Returns:

numpy.ndarray: The decay rate, 1/s, the shape of density.

Raises:

DataError: If a density is negative or not finite.

frequency: Float[ndarray, 'm']#

gamma_broadening: float#

gamma_constant: float#

gamma_dicke: float#

gamma_doppler: float#

index: int#

isotropic: Float[ndarray, 'm']#

line_ids: tuple[str, ...]#

lines: tuple[int, ...]#

response(time, density, component='parallel')[source]#

Return the group’s share of the response at a density.

Parameters:

timearray_like: Delay after the impulse, s (zero before it).
densityfloat: Total number density, m^-3, >= 0.
component{“parallel”, “isotropic”, “anisotropic”, “a”, “b”}, optional: The part of the response.

Returns:

numpy.ndarray: The group’s response, m^5 V^-2 s^-1, the shape of time.

shift: float#

property shifted: bool#

Whether the group’s frequencies move with the density.

Returns:

bool: True where shift is not 0.

optmat.gas.raman_response.placzek_teller_q(j)[source]#

Return the Placzek-Teller coefficient of the Q lines, \(b_{J,J}\).

The share of a level’s anisotropic scattering that keeps \(J\), \(J(J+1)/[(2J-1)(2J+3)]\); with \(b_{J+2,J}\) and \(b_{J-2,J}\) the three sum to one. It is 0 for \(J = 0\) and tends to 1/4.

Parameters:

jnumpy.ndarray: Rotational levels, >= 0.

Returns:

numpy.ndarray: \(b_{J,J}\).

Examples

>>> [f"{b:.4f}" for b in placzek_teller_q(np.array([0, 1, 2, 50]))]
['0.0000', '0.4000', '0.2857', '0.2501']

optmat.gas.raman_response.raman_response(gas, temperature, *, wavelength=None, population_floor=1e-12)[source]#

Return the Raman response of a gas or a mixture at a temperature.

Parameters:

gasGas or str or mapping of str to float: A molecular gas ("N2"), a mixture named in raman_response.toml ("dry air"), or mole fractions by species (atoms take part as collision partners only).
temperaturefloat: Temperature, K, > 0: the populations and the widths.
wavelengthfloat, optional: Vacuum wavelength of the pump, m, at which the vibrational strengths are dispersed (Bischel & Black’s law, TC-542); by default as curated.
population_floorfloat, optional: Lines from levels less populated than this fraction are left out.

Returns:

GasRamanResponse: The response, with its density dependence.

Raises:

DataError: If a species has no Raman parameters or choices, or a collision partner has no broadening coefficient.

Warns:

ModelRangeWarning: If the temperature is outside that of the width measurements.

Examples

>>> from optmat.gas.linewidths import AMAGAT
>>> air = raman_response("dry air", 295.0, wavelength=800e-9)
>>> sorted(set(air.species))
['N2', 'O2']
>>> f"{air.rotational_nonlinear_index(AMAGAT) * 1e23:.2f}"
'3.22'

optmat.gas.raman_response.raman_response_status(gas)[source]#

Return the status a gas’s Raman response would have, without building it.

The status and its reason are those of raman_response()’s result at any temperature and wavelength, read from the curated choices alone: a propagation code can ask whether a gas’s response is validated or provisional, or whether it has none, without computing the lines. The collision partners are not checked: a mixture whose constituents lack broadening coefficients by one another (CO2 with N2) has a status here, and raman_response() refuses it.

Parameters:

gasGas or str or mapping of str to float: As for raman_response().

Returns:

tuple of (str, str) or None: The status (validated, provisional, …) and its reason (empty for validated); None where no constituent is Raman-active, as for the noble gases, which have no Raman response at all.

Raises:

DataError: As raman_response() does for a molecule without curated choices or a composition it refuses.

Examples

>>> raman_response_status("N2")
('validated', '')
>>> raman_response_status("CO2")[0]
'provisional'
>>> raman_response_status("Ar") is None
True