dakka_2018#
M. A. Dakka, G. Tsiminis, R. D. Glover, C. Perrella, J. Moffatt, N. A. Spooner, R. T. Sang, P. S. Light and A. N. Luiten, “Laser-based metastable krypton generation”, Phys. Rev. Lett. 121, 093201 (2018)
Source record · Catalogue · Review register
DOI: 10.1103/PhysRevLett.121.093201
Source kind: measurement
Recorded technique: Two-photon excitation of krypton (0.05 mbar, in a quartz cell) from the ground state to the 2p6 level (Paschen; 4p5 5p[3/2]2) with a frequency-doubled optical parametric oscillator near 215 nm (the OPO’s output at about 429 nm measured with a spectrometer): 5 ns pulses of up to 2 mJ, a 200 GHz bandwidth, focused by a 75 mm CaF2 lens to a 100 um spot (peak intensity about 1 GW cm-2). The 760 nm (2p6 -> 1s5) and 819 nm (2p6 -> 1s4) laser-induced fluorescence imaged on an EMCCD camera (collection efficiency 0.1 %) gives the metastable fraction per atom against detuning and pulse energy (Fig. 5). sigma_0^(2) and the 2p6 photoionisation cross section sigma_ei are the two free parameters of a fit (least root-mean-square error) of a four-level density-matrix model (ground, 2p6, 1s5, ion; Eq. 1), with the two-photon Rabi frequency Omega^(2) = sqrt(2 sigma_0^(2) / pi) I / (hbar omega_0) (Eq. 2), a photoionisation rate R = sigma_ei I / (2 hbar omega_0) (Eq. 3), a phase-diffusion model of the laser’s 200 GHz bandwidth (Eq. 4, Gaussian lineshape parameter b ~ 3), spontaneous decay, collisions (including Penning ionisation) and the branching ratio.
Materials in structured entries: Kr
Dataset quantities: excited_state_photoionization_cross_section, two_photon_excitation_cross_section
Contents: 2 datasets; 0 formulas.
Curation notes#
The library holds the submitted version: arXiv:1805.05669v1 (15 May 2018), 5 pages (PDF pp. 2-6) after the University of Adelaide repository’s cover (PDF p. 1), which names the published article, Phys. Rev. Lett. 121(9), 093201 (2018). Identity checked against the cover and the first page (title, authors). The numbers of the published version are not checked: shekhtman_2020 quotes this sigma_0^(2) as ‘5.2 +- 2.2 x 10^-35 cm4’ citing the published article, while this copy prints 5.2 +- 2.1 (and drag_2021 quotes 5.2e-43 m4 +- 40 %, which fits 2.1).
WHAT IS TAKEN (tools/extract/dakka_2018.py). Table I (PDF p. 5), ‘This work’: sigma_0^(2) = 5.2 +- 2.1 x 10^-35 cm4 for the ground-2p6 two-photon transition, and sigma_ei = 3.8 +- 1.7 x 10^-18 cm2, the photoionisation cross section of the 2p6 level by the same 215 nm light. Neither error has a stated level or origin (the fit’s, the calibration’s).
DEFINITIONS. sigma_0^(2) is defined through the Rabi frequency, Eq. (2), which is drag_2021’s Eq. (11), Omega = sqrt(2 sigma-bar / pi) Phi, derived there from the cross section integrated over the two-photon angular frequency 2 omega (drag_2021, Eqs. 8-11; its footnote: ‘This is formula (2) of Dakka et al. (2018)’): the frequency-integrated cross section with the profile normalised in angular frequency. The polarisation is not stated. The photon statistics are not measured: the 200 GHz light is modelled by phase diffusion only (no intensity fluctuations, so G2(0) = 1 in the model). DOUBT: Eq. (3) writes the ionisation rate as sigma_ei I / (2 hbar omega_0), with omega_0 ‘the laser frequency’ (under Eq. 2); the photon flux of the ionising light is I / (hbar omega_0), so as printed sigma_ei would be twice the usual one-photon cross section. Whether that factor 2 is a misprint of the submitted version or was used in the fit cannot be told from the paper; the value is kept as a check.
NOT TAKEN. The branching ratio of 2p6 to the metastable 1s5, beta = 75 +- 4 % (from the 760 and 819 nm fluorescence intensities; ‘The uncertainty arises from uncertainty in the wavelength-dependent quantum efficiency of the spectrometer CCD’), and the literature average 76 +- 3 %: no quantity of the vocabulary holds a branching ratio. Table I’s ‘Literature’ sigma_0^(2), 2.4 +- 0.8 x 10^-35 cm4, is xenon’s ground-2p6 transition from Kroll and Bischel (kroll_1990; ‘Not directly comparable’): it is their as-measured product sigma_tot G2(0) (2.4), not their G2-corrected sigma_tot (1.7) (checked by the script against kroll_1990’s record). The ‘Literature’ sigma_ei, 3.3 x 10^-18 cm2, is ‘Calculated from’ H. Hyman, Appl. Phys. Lett. 31, 14 (1977) (not in the library), by a calculation the paper does not give. Figs. 2-6 (spectra, images, model curves). The metastable-production efficiencies (2 % per pulse measured, up to 30 % modelled).
Recorded bibliographic identity status: VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
dakka_2018/sigma0_2p6#
{
"id": "sigma0_2p6",
"material": "Kr",
"file": "Kr/dakka_2018__sigma0_2p6.csv",
"table": "tbl_599c680c31e3",
"quantity": "two_photon_excitation_cross_section",
"unit": "cm4",
"scale": 1e-35,
"abscissa": "label",
"use": "primary",
"uncertainty": {
"column": true,
"level": "not stated"
},
"parameters": {
"frequency_variable": "angular",
"polarization": "not stated",
"photon_statistics": "not measured: the 200 GHz-wide OPO light is modelled by phase diffusion without intensity fluctuations (G2(0) = 1 in the model)",
"method": "fit of a four-level density-matrix model to the 760 nm fluorescence against detuning and pulse energy",
"definition": "through the two-photon Rabi frequency, Omega^(2) = sqrt(2 sigma_0^(2) / pi) I / (hbar omega_0) (Eq. 2), drag_2021's Eq. (11): the cross section integrated over the two-photon angular frequency",
"pulse_ns": 5,
"bandwidth_ghz": 200
}
}
Table I (PDF p. 5), ‘This work’: sigma_0^(2) of the ground (4p6 1S0) to 2p6 (4p5 5p[3/2]2, J = 2) transition, excited near 215 nm (the paper prints no closer wavelength). Fitted with the density-matrix model (record technique). The +- has no stated level.
dakka_2018/photoionization_2p6#
{
"id": "photoionization_2p6",
"material": "Kr",
"file": "Kr/dakka_2018__photoionization_2p6.csv",
"table": "tbl_599c680c31e3",
"quantity": "excited_state_photoionization_cross_section",
"unit": "cm2",
"scale": 1e-18,
"abscissa_unit": "nm",
"use": "check",
"uncertainty": {
"column": true,
"level": "not stated"
},
"parameters": {
"initial_level": "2p6 (Paschen) = 4p5 5p[3/2]2, J = 2, two-photon excited from the ground state",
"method": "fit of a four-level density-matrix model to the 760 nm fluorescence against detuning and pulse energy",
"definition": "R = sigma_ei I / (2 hbar omega_0) (Eq. 3), omega_0 the laser frequency, as printed"
}
}
Table I (PDF p. 5), ‘This work’: sigma_ei of the 2p6 level, ionised by a third photon of the same light; the wavelength as printed, ‘215 nm’ (nominal). A check, because Eq. (3) defines it with I / (2 hbar omega_0), half the photon flux (record notes). The +- has no stated level.
Formulas#
No formulas are recorded.
Corrections#
No dataset errata are recorded in this source record.
Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.