balakrishnan_1992#
A. Balakrishnan, V. Smith and B. P. Stoicheff, “Dissociation energy of the hydrogen molecule”, Phys. Rev. Lett. 68, 2149 (1992)
Source record · Catalogue · 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#
{
"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#
{
"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+#
{
"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 review register for the checks and decisions.