balakrishnan_1992 ================= A\. Balakrishnan, V\. Smith and B\. P\. Stoicheff, "Dissociation energy of the hydrogen molecule", Phys\. Rev\. Lett\. 68, 2149 \(1992\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1103/PhysRevLett\.68\.2149 `__ **Source kind:** measurement **Recorded technique:** Single\-photon fluorescence\-excitation spectroscopy of H2 near 84\.5 nm\: tunable XUV at 2 nu1 \+ nu2 by four\-wave mixing in a pulsed Kr jet, nu1 \(doubled from about 424 nm, 0\.2 cm^\-1, about 15 kW\) resonant with the two\-photon level 4p5 5p\[1/2\]0 of Kr and nu2 \(single\-mode dye laser near 414 nm, 0\.02 cm^\-1, about 55 kW\) scanned, both focused by a 25 cm lens; 4 ns XUV pulses crossing an H2 jet 50 mm below its nozzle\. The H\(2s\) atoms from dissociation above the second limit were quenched by a field of about 150 V/cm switched on about 200 ns after the pulse, and the delayed Lyman\-alpha fluorescence recorded; nu2 calibrated on uranium optogalvanic lines, 2 nu1 in a separate third\-harmonic experiment \(p\. 2151\)\. The threshold by least\-squares linear extrapolation of the onset \(two spectra of twelve scans each\)\. **Materials in structured entries:** H2, H2\+ **Dataset quantities:** dissociation\_energy **Contents:** 3 datasets; 0 formulas. Curation notes -------------- Phys\. Rev\. Lett\. 68\(14\), 2149\-2152 \(6 April 1992\) = PDF pages 1\-4 \(journal page = PDF page \+ 2148\); a scan with a text layer\. Identity checked against the first page \(VOLUME 68, NUMBER 14, PHYSICAL REVIEW LETTERS, 6 APRIL 1992; received 11 December 1991; Balakrishnan, Smith and Stoicheff, Toronto\) on 2026\-10\-09\. Numbers read on the rendered pages \(pp\. 2149, 2151\) and Table I's image\. THE SAME MEASUREMENT AS balakrishnan\_1994\. That paper \(Phys\. Rev\. A 49, 2460 \(1994\)\) reports these H2 spectra in full \(its Table III cites this Letter as \[4\]\), adds D2, and halves the H\(1s\) hyperfine allowance \(0\.024 here, 0\.013 there\); its D0\(H2\), D\_L and D0\(H2\+\) are the primary datasets\. Here every dataset is check, so that the one measurement is not counted twice\. WHAT IS TAKEN \(check\)\. \(1\) Table I \(p\. 2151, tbl\_8f13575d8bbe; tools/extract/ balakrishnan\_1992\.py\), the 'Present' row\: D0\(H2\) = 36 118\.11\+\-0\.08 cm^\-1 \(also the abstract and the displayed equation, p\. 2151\)\. The text's budget\: 'D0\(H2\) = 36 118\.11\+\-0\.064 cm\-1, which includes an uncertainty of 0\.024 cm\-1, arising from the hyperfine splitting', then \+\-0\.04 for the calibration of 2 nu1 and nu2 and 0\.03 for a Doppler shift \(Delta theta = 1\.8 degrees\), 'combined in quadrature' to \+\-0\.08 \(sqrt\(0\.064^2 \+ 0\.04^2 \+ 0\.03^2\) = 0\.081\)\. \(2\) Text, inline\: the second dissociation limit 118 377\.06\+\-0\.04 cm^\-1 \(abstract; p\. 2151\) and D0\(H2\+\) = 21 379\.36\+\-0\.08 cm^\-1 \(abstract; p\. 2152\), from D0\(H2\) \+ IP\(H\) \- IP\(H2\) with IP\(H\) = 109 678\.764\+\-0\.01 and IP\(H2\) the average of 124 417\.501\+\-0\.017 \(Jungen et al\. 1990\) and 124 417\.524\+\-0\.015 \(McCormack et al\. 1989\), which are liu\_2009's jungen\_1990\_H2 and mccormack\_1989\_H2\. balakrishnan\_1994 gives 21 379\.37 with a different pair of ionisation energies\. CHECKED \(the script\)\: 118 258\.57 \+ 118\.49 = 118 377\.06; 118 377\.06 \- 82 258\.95 = 36 118\.11, Table I's value; 36 118\.11 \+ 109 678\.764 \- 124 417\.5125 = 21 379\.3615\. The uncertainties are printed '\+\-' without a level\. KRYPTON\. The Letter calibrates 2 nu1 as '94 093\.00\+\-0\.04 cm\-1 for the Kr level 5p\[0,1/2\]0 \(in agreement with, but more precise than, an earlier value \[12\] of 94 092\.924\+\-0\.15 cm\-1\)' \(Kaufman and Humphreys 1969; p\. 2151\), at about 15 kW peak power\. NOT TAKEN\: balakrishnan\_1994 \(p\. 2466\) shows this value to be ac Stark shifted \(the level, extrapolated to zero intensity, is 94 092\.93\+\-0\.05\)\: a light\-shifted resonance, not a level energy\. The Letter prints no light\-shift coefficient\: brandi\_2002 cites it \(with the 1994 paper\) for '2\.6\(1\.1\) Hz \(W cm\-2\)\-1', which is only in the 1994 paper \(balakrishnan\_1994, ls\_5p12\_0\)\. NOT TAKEN\: Table I's other rows \(Herzberg \[3\] 36 118\.3; Stwalley \[4\] 36 118\.6\+\-0\.5; McCormack and Eyler \[5\] 36 118\.26\+\-0\.20; the theory of Kolos, Szalewicz and Monkhorst with Dressler and Wolniewicz \[1, 2\], 36 118\.09\+\-0\.10, quoted in the text as 36 118\.088 with \+\-0\.10\)\: reproduced, and taken from balakrishnan\_1994's Table III; the threshold above J'' = 1, 118 258\.57\+\-0\.04 \(not from the ground level\); the para\-H2 'preliminary value of 118 377\.0' \(p\. 2151\); the H\(1s\) hyperfine splitting 0\.047 cm^\-1 \(p\. 2150\); Herzberg's upper bound 118 377\.6, Stwalley's limit 118 377\.7\+\-0\.5 and McCormack and Eyler's onset 118 377\.2\+\-0\.20 \(p\. 2149; reproduced limits\); the figures \(spectra, no further numbers\)\. No two\-photon cross section, line width or lifetime is given\. **Recorded bibliographic identity status:** VALIDATED\_WITH\_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents. Datasets -------- balakrishnan\_1992/d0\_H2 ~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "d0_H2", "material": "H2", "file": "H2/balakrishnan_1992__d0_H2.csv", "table": "tbl_8f13575d8bbe", "quantity": "dissociation_energy", "unit": "cm-1", "abscissa": "label", "use": "check", "parameters": { "kind": "D0", "products": "H(1s) + H(1s)", "initial_state": "X 1Sigma_g+ (v = 0, J = 0), para-H2" }, "uncertainty": { "column": true, "level": "not stated" } } Table I \(p\. 2151\), 'Present'\: '36 118\.11 ± 0\.08'\. The measurement reported in full by balakrishnan\_1994 \(d0\_H2, the primary dataset\), so check\. Level not stated\. balakrishnan\_1992/dl\_H2 ~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "dl_H2", "material": "H2", "table": "text", "quantity": "dissociation_energy", "unit": "cm-1", "abscissa": "label", "use": "check", "parameters": { "kind": "D0", "products": "H(1s) + H(2s)", "initial_state": "X 1Sigma_g+ (v = 0, J = 0)" }, "uncertainty": { "column": true, "level": "not stated" } } 1 inline points in the source record. Abstract and p\. 2151\: the second dissociation limit, 118 258\.57\+\-0\.04 cm^\-1 above J'' = 1 \(two spectra of twelve scans each\) plus the rotational spacing 118\.49 \(Foltz et al\.\)\. The same value as balakrishnan\_1994's dl\_H2 \(primary\), so check\. Level not stated\. balakrishnan\_1992/d0\_H2\+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "d0_H2+", "material": "H2+", "table": "text", "quantity": "dissociation_energy", "unit": "cm-1", "abscissa": "label", "use": "check", "parameters": { "kind": "D0", "products": "H(1s) + H+", "initial_state": "X 2Sigma_g+ (v+ = 0, N+ = 0)" }, "uncertainty": { "column": true, "level": "not stated" } } 1 inline points in the source record. Abstract and p\. 2152\: D0\(H2\+\) = D0\(H2\) \+ IP\(H\) \- IP\(H2\) = 21 379\.36\+\-0\.08 cm^\-1, with IP\(H2\) the average of Jungen et al\.'s 124 417\.501\+\-0\.017 and McCormack et al\.'s 124 417\.524\+\-0\.015; 'in good agreement with the theoretical value \[15,16\] of 21 379\.348'\. Derived from other laboratories' ionisation energies, and superseded by balakrishnan\_1994's 21 379\.37 \(d0\_H2\+\), so check\. Level not stated\. 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.