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 `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1016/0009\-2614\(80\)80558\-6 `__ **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 :doc:`review register ` for the checks and decisions.