chen_1980#

C. H. Chen, G. S. Hurst and M. G. Payne, “Direct counting of Xe atoms”, Chem. Phys. Lett. 75, 473-477 (1980)

Source record · Catalogue · Review register

Source kind: measurement

Recorded technique: Resonance ionisation of xenon (partial pressure 10^-8 to 10^-6 Torr in a cell at about 10^-6 Torr): (2+1) ionisation through 5p5 6p by a single beam, a Nd:YAG-pumped red dye laser (645-675 nm, about 40 mJ, about 5 ns) frequency-doubled in KDP and mixed with the 1.06 um fundamental, tunable over 246-258 nm, about 1 mJ and about 4 ns at a two-photon resonance (‘252.6 or 249.6 nm’), focused by a 13.5 cm lens; the ions counted on a channeltron in analogue mode (and through a quadrupole mass filter). The ‘resonance widths being limited by the laser linewidth (fwhm = 0.4 A)’ (Fig. 2). The two-photon rate R and the ionisation rate Gamma_I from a fit of the rate-equation ionisation probability (Eq. 1), integrated over a doughnut-shaped focus with a square pulse (Eq. 4), to the ion signal against the square of the pulse energy (Fig. 3, ‘at 252.6 nm’).

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes#

Chem. Phys. Lett. 75(3), 473-477 (1 November 1980) = PDF pages 1-5 (journal page = PDF page + 472); a scan with a text layer. Identity checked against the first page (CHEMICAL PHYSICS LETTERS, Volume 75, number 3, 1 November 1980; received 22 July 1980; Oak Ridge National Laboratory) on 2026-10-09. Every number below was read on the rendered pages (pp. 474-476).

NOTHING IS TAKEN AS DATA. The paper’s results are rate coefficients of one apparatus, in W/cm2: ‘Fig. 3 is reproduced very well by the choice Gamma_I = 3I and R ~ 2 x 10^-9 I^2’ (p. 476), I the power density in W/cm2, R and Gamma_I in s-1. Neither is a quantity of the vocabulary as printed: - R is the on-resonance two-photon rate for a 0.4 A (FWHM) laser, in the rate formalism R = 4 |Omega(0,2)|^2 / Gamma_L (Eq. 2, Gamma_L the laser bandwidth): a line-centre coefficient whose conversion to two_photon_excitation_cross_section (TC-872) needs a line shape, a frequency variable and the photon statistics, which the paper does not state; nor does it say which spectral width the fit assumed. - Gamma_I = 3I is the photoionisation rate of the two-photon-excited level; with Gamma_I = sigma_I I / hbar omega (the form of Payne et al. below) it corresponds to sigma_I = 3 hbar omega = 2.4 x 10^-18 cm2 at 252.6 nm: derived here, not printed, so not data. The theoretical ‘photoionization cross section to be ~2.0 x 10^-18 cm2’ is Pindzola’s (Ref. 11, a private communication), from which the paper gives ‘Gamma_I ~ 2.4/(W/cm2)’ (2.0e-18 / hbar omega is 2.5). - The theoretical R ~ 3.1 x 10^-9 I^2 (p. 475) is checked: Omega(0,2) ~ 2 x 10^17 I / Delta omega with Delta omega ~ 8 x 10^15 s-1 is 25 I, and 4 (25 I)^2 / (8 x 10^11) = 3.1 x 10^-9 I^2. The later ‘two-photon Rabi frequency is ~20 I’ (p. 476) is a rounder value of the same.

WHICH LEVEL. The paper puts the measurement at 252.6 nm (p. 474: ‘During the experiment the 252.6 nm radiation was focused’; Fig. 3’s caption, ‘at 252.6 nm’), the 6p[3/2]2 resonance of its Fig. 2 (peaks near 2496 and 2525 A, both 0.4 A wide). The same group’s later accounts put it at 2496 A, the 6p[1/2]0 resonance: M. S. Pindzola, M. G. Payne and W. R. Garrett, Phys. Rev. A 24, 3115 (1981) (pindzola_1981b, p. 3118: ‘W = 2.4 x 10^-23 I^2 where I is in ergs/cm2 sec’, i.e. 2.4 x 10^-9 in W/cm2, for 6p (J = 0), ‘line width ... somewhere between 0.05 and 0.01 A’, their Table II using 0.05 and 0.10 A); M. G. Payne, C. H. Chen, G. S. Hurst and G. W. Foltz, Adv. At. Mol. Phys. 17, 229 (1981) (payne_1982, pp. 246-247: 6p[1/2]0 at 2496 A, a dye laser of 0.16 A and ‘the linewidth of the 2496 A beam was between 0.05 and 0.1 A’, K = 2 x 10^-9 s-1 W-2 cm4 and sigma_1 = 3 x 10^-18 cm2, a lens of 15 cm; their Figs. 2 and 3 are the signal against the square of the energy and the depletion with time, mu Delta V = 2 x 10^-4 cm3, as this paper’s Figs. 3 and 4). So the level, the laser width (0.4 A here, 0.05 to 0.1 A there) and the coefficient (2 x 10^-9 here and in Payne et al., 2.4 x 10^-9 in Pindzola et al.) of this one measurement are reported differently by its authors; the record cannot resolve them.

FINDINGS. raymond_1984 (Table I) lists this paper as alpha = 96 cm4/J2 for 6p[1/2]0, ‘inferred from their measured transition rates’, the laser width ‘assumed to be 0.01 A’; kroll_1990 (TC-890) lists it as sigma_tot G2(0) = 6.1 x 10^-35 cm4 for 2p5 = 6p[1/2]0, which is 96 cm4/J2 times (hbar omega)^2 at 249.63 nm (6.08 x 10^-35). The 96 is reproduced within 1.5 % from R / I^2 = 2 x 10^-9 with a 0.01 A Gaussian laser and xenon’s two-photon Doppler width (0.086 cm-1) in a unit-area profile in angular frequency: 97.4 at 249.63 nm, 95.3 at 252.48 nm. The 0.01 A is 40 times narrower than this paper’s 0.4 A and 5 to 10 times narrower than Payne et al.’s 0.05-0.1 A (it matches Pindzola et al.’s text, whose table uses 0.10); with 0.08 A the same step gives 730 cm4/J2 (4.6 x 10^-34 cm4 as alpha (hbar omega)^2), with 0.4 A about 2 x 10^-33 cm4. Pindzola et al. themselves infer 2.73 and 5.46 x 10^-12 cm4/erg2 (273 and 546 cm4/J2) for 0.05 and 0.10 A with their own G = (8 ln 2 / pi)^(1/2) / Delta_L. So the kroll_1990 and raymond_1984 rows rest on a width that no account of the measurement gives except as Pindzola et al.’s slip, and their 6.1 x 10^-35 cm4 is not a value of this paper.

TWO-PHOTON DATA CITED, NOT IN THE LIBRARY: C. H. Chen and G. S. Hurst, Proc. 11th Int. Quantum Electronics Conf. (1980), p. 659 (Xe resonance ionisation).

Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.

Datasets#

No datasets are recorded.

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.