ditchburn_1954#
R. W. Ditchburn and D. W. O. Heddle, “Absorption cross-sections in the vacuum ultra-violet. II. The Schumann-Runge bands of oxygen (2000 to 1750 A)”, Proc. R. Soc. Lond. A 226, 509 (1954)
Source record · Catalogue · Review register
Source kind: measurement
Recorded technique: Photographic absorption spectrophotometry of the unbroadened Schumann-Runge bands with the 1 m concave-grating vacuum spectrograph of part I (slit 5e-4 cm, resolution insufficient to separate the rotational structure at the heads; P(J) and R(J + 2) unresolved for v’ < 8, resolved for v’ = 8-15), a d.c. hydrogen discharge, Ilford Q1 plates and a Moll microphotometer; paths 205 +- 1 cm (O2 at 0.3-760 mm Hg in the spectrograph) and 4.90 +- 0.05 cm (250-750 mm Hg). The minimum transmission of each line was converted to a peak cross section through computed curves of transmission against sigma_0 n L and the damping ratio (Fig. 3, Appendix 2: the grating’s instrumental function, a Voigt profile with the Doppler breadth at 20 C), with the radiation damping ratio taken from an assumed f-sum and iterated until the f-sum of the derived band oscillator strengths agreed (Eqs. 1-10, pp. 513-514); the rotational populations from a weighted Boltzmann factor (Eq. 10) (pp. 510-514, 520).
Materials in structured entries: O2
Dataset quantities: oscillator_strength
Contents: 3 datasets; 0 formulas.
Curation notes#
Journal pages 509-521 = PDF pages 2-14 (page 1 is the JSTOR cover; page 2 opens with the end of the preceding paper’s references, and page 14 continues with the next paper, Skyrme’s). Identity checked against the first page (PDF page 2): Ditchburn and Heddle, Proc. R. Soc. A 226, 509, received 29 June 1954. O2 only. Part I is ditchburn_1953.
Table 1 (p. 514): the oscillator strengths f of the bands (v’, 0), v’ = 0-20, ‘the values for bands with v’ = 1, 18, 19 and 20 being extrapolated’ (p. 514). The f-sum of the discrete transitions is 0.044 (p. 515) and ‘The total oscillator strength (including the continuum) is found to be 0.259’ (abstract, p. 509), the continuum’s 0.215 being part I’s (p. 513, reproduced; recorded in ditchburn_1953). Accuracy: ‘the total errors are estimated to be less than 20 %’ (p. 515, said of the f-sum after the extrapolation to high v’); ‘The oscillator strengths for these bands [v’ = 2, 3, 4] are probably the least accurate’ (p. 516); the standard deviation of the relative line intensities within bands 20 % (p. 514). Temperature: room temperature; the analysis takes the Doppler breadth for 20 C (Eq. 23, p. 520); the fraction of molecules with v’’ > 0 is 5.7e-4 (p. 509).
These band strengths are not usable: Bethke (1959, bethke_1959, Table I column six, which reproduces all sixteen values v’ = 2-17 exactly, and its remainder 2276e-5 = f(18,0) + f(19,0) + f(20,0) and total 4450e-5, both reproduced by the sums of this table, checked 2026-09-25) finds them 80 to 110 times his own for (2,0)-(8,0) and the band sum 140 times his 0.000314, and they imply an electronic f_el of 0.8 to 17 against 0.030-0.55 expected; Matsui et al. (2003, matsui_2003) find (12,0)-(17,0) 15-28 % below Bethke’s. The cause is not identified in the library papers; the analysis here derived the line breadths from an assumed f-sum through radiation damping alone (Eqs. 2, 3, 9) and neglected collision broadening at the long-path pressures (p. 516). All datasets are therefore excluded, kept for the record. bethke_1959/ditchburn_heddle is a reproduction of this table.
Not extracted: Table 2 (p. 516), the cross sections Q for deactivating collisions of the upper state per (v’, J’) (Eq. 11, rho_c = 5.15e11 p Q; italic values measured with the 4.90 cm path, roman values calculated for rotational deactivation, the typeface not kept by the extraction), not optical data. Figure 5 (relative f, f(0,11) = 100, against Pillow’s theory) and the mean relative line intensities (Fig. 4) are figures only. Also stated: the dissociation limit 57140 +- 20 cm^-1 (‘K’), D0 = 5.12 eV (p. 511); the note added in proof (p. 521) takes Brix and Herzberg’s 5.1148 +- 0.002 eV and 57128 +- 5 cm^-1 as definitive. Bethke’s comparison is the check.
Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
ditchburn_1954/band_f#
{
"id": "band_f",
"material": "O2",
"file": "O2/ditchburn_1954__band_f.csv",
"table": "tbl_2b2a1247ae97",
"quantity": "oscillator_strength",
"abscissa": "label",
"use": "excluded",
"excluded_rows": {
"(1,0)": "extrapolated (p. 514)",
"(18,0)": "extrapolated (p. 514)",
"(19,0)": "extrapolated (p. 514)",
"(20,0)": "extrapolated (p. 514)"
}
}
Table 1: band oscillator strengths f(v’, 0) of the Schumann-Runge system, v’ = 0-20 (index v’), each printed with its own power of ten (value column in E notation). Excluded: 80-140 times the pressure-broadened photoelectric values of bethke_1959 and matsui_2003 (see the record’s notes). v’ = 1, 18, 19, 20 are the paper’s extrapolations (excluded_rows). No per-band uncertainty; the v’ = 2-4 values ‘probably the least accurate’ (p. 516). Bands’ wavelengths not tabulated.
ditchburn_1954/band_sum#
{
"id": "band_sum",
"material": "O2",
"table": "text",
"quantity": "oscillator_strength",
"abscissa": "label",
"use": "excluded"
}
1 inline points in the source record.
p. 515: ‘The f-sum for the discrete transitions is 0.044’ (Table 1 sums to 0.04450 with the extrapolated bands; Bethke prints it as 4450e-5). Index 0 marks the first band of the sum. Excluded with band_f (140 times bethke_1959’s 0.000314).
ditchburn_1954/total_f#
{
"id": "total_f",
"material": "O2",
"table": "text",
"quantity": "oscillator_strength",
"abscissa": "label",
"use": "excluded",
"uncertainty": {
"relative": 0.2,
"level": "bound"
}
}
1 inline points in the source record.
Abstract (p. 509) and p. 516 (‘For Sigma f = 0.259’): the total oscillator strength of the Schumann-Runge transition, the continuum’s 0.215 (ditchburn_1953, part I) plus the band sum 0.044. ‘total errors ... less than 20 %’ (p. 515), recorded as a bound. Excluded: the band part is about 140 times too large (bethke_1959), so the total overstates the system by about 0.044; the continuum part is in ditchburn_1953/continuum_f.
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.