ditchburn_1953 ============== R\. W\. Ditchburn and D\. W\. O\. Heddle, "Absorption cross\-sections in the vacuum ultra\-violet\. I\. Continuous absorption of oxygen \(1800 to 1300 A\)", Proc\. R\. Soc\. Lond\. A 220, 61 \(1953\) `Source record `__ · :doc:`Catalogue ` · :doc:`Review register ` DOI: `10\.1098/rspa\.1953\.0171 `__ **Source kind:** measurement **Recorded technique:** Photographic absorption spectrophotometry \(Ilford Q1 plates\) with a 1 m concave\-grating vacuum spectrograph \(a small fluorite Cario\-Schmidt\-Ott spectrograph in preliminary work\) and a water\-cooled capillary hydrogen discharge \(many\-line molecular spectrum\); intensity reduced in a known ratio by grids \(transmission calibrated photographically against a rotating sector\); stray radiation reduced to 'a negligible fraction' by diaphragms\. Paths 205 \+\- 1 cm \(the spectrograph filled with O2, 1\-12e\-3 mm Hg\) and 0\.043 \+\- 0\.0025 cm \(a brass cell with fluorite windows, 5\-200 mm Hg\); O2 from cylinders \(CO2 and water removed\) or from heated permanganate\. About fifty emission lines between 1360 and 1670 A, on average ten measurements each; Beer's law tested with path ratio 5000\:1 and pressure ratio 200000\:1, 'No systematic deviations' \(pp\. 62\-67\)\. **Materials in structured entries:** O2 **Dataset quantities:** absorption\_cross\_section, oscillator\_strength **Contents:** 5 datasets; 0 formulas. Curation notes -------------- Journal pages 61\-70 = PDF pages 2\-11 \(page 1 is the JSTOR cover; page 2 opens with the end of the preceding paper's references\)\. Identity checked against the first page \(PDF page 2\)\: Ditchburn and Heddle, Proc\. R\. Soc\. A 220, 61, received 24 April 1953\. O2 only\. Quantity \(Eq\. 1, p\. 61\)\: ln\(I0/I\) = alpha p l = N sigma\_nu p l, 'p is the pressure \(reduced to 0 C\) in atmospheres and N = 2\.705 x 10^19 cm^\-3'\: alpha \(cm^\-1\) is the natural\-log absorption coefficient at 1 atm and 0 C\. The datasets keep the printed alpha with scale = 1e18 / 2\.705e19 = 0\.0369686 to the cross section in Mb, the paper's own conversion\: its maximum alpha 490 cm^\-1 'corresponds' to 1\.81e\-17 cm^2 \(490 / 2\.705e19 = 1\.811e\-17\)\. The ideal\-gas Loschmidt density at 0 C and 1 atm, 2\.6868e19 cm^\-3, is 0\.67 % lower than the paper's N, so the physical cross section alpha / n0 would be 0\.68 % larger than these values \(well inside the stated errors; noted for review\)\. Temperature of the gas not stated \(room temperature\)\. Wave numbers are vacuum wave numbers \(69000 cm^\-1 = 1449 A, the paper's '1450 A'\)\. Accuracy \(p\. 69\)\: 'the average probable error of a single observation is rather less than 60 cm^\-1\. The limits of error given in the table are based on the assumption that the average of n observations is subject to an error of \+\-60 n^\-1/2 cm^\-1\. The observational error calculated in this way is probably a little too high and is certainly correct within a factor of 2\.' Check \(2026\-09\-25\)\: the printed errors of Table 1 do not follow 60 n^\-1/2; they follow about 80 n^\-1/2 \(n = 12\: 23; 24\: 16; 74\: 9; 56\: 11; 64\: 10; 21\: 17; 39\: 13; 23\: 17; 20, 19\: 18\), with 20 printed for every group of 15\-17 observations except the 64108 group \(16 observations, printed \+\-16 where 80 n^\-1/2 gives 20\)\. The printed errors are kept as the paper's probable errors\. Check of the group means \(2026\-09\-25\)\: the observation\-weighted means of each group's lines \(columns 2 and 3 with the bracketed numbers of observations\) reproduce columns 4 and 5 for 20 of the 21 groups \(to 0\.5 cm^\-1 in alpha; the 69484 group's wave number comes out 69500\)\. The group 64060\-63810 \(306 \(7\), 307 \(6\), 228 \(3\)\) gives 63919 cm^\-1 and 291\.8 cm^\-1 against the printed 64108 and 277 \+\- 16\: a printed mean wave number above every line of its group is impossible for a weighted mean, so the row as printed is inconsistent; no single misprint explains both columns and no erratum is made\. Doubt queued \(TC\-213\)\. Text values \(pp\. 61, 67, 70\)\: the maximum 'is 490 cm^\-1, and the corresponding maximum cross\-section is 1\.81 \+\- 0\.1 x 10^\-17 cm^2 at 69000 cm^\-1 and 1450 A'; half\-value at 63800 and 73000 cm^\-1 \(abstract\: 1567 and 1370 A, not data\)\. Note added in proof \(p\. 70\)\: 'Making a reasonable extrapolation of the curve in figure 4, we obtain an f\-value of 0\.215 \+\- 0\.020' \(against Watanabe et al\.'s 0\.161, watanabe\_1953, and Ladenburg and Van Voorhis's 0\.193, ladenburg\_1933\)\. The smooth curve of Fig\. 4 and the points of Schneider \(1937\) and Ladenburg and Van Voorhis \(1933\) plotted with it are figures only\. Comparison \(p\. 69\)\: Watanabe, Inn and Zelikoff's preliminary maximum 380 cm^\-1 'at 71000 cm^\-1' \(watanabe\_1952, which prints 1420 A, 70420 cm^\-1\) is '25 % lower' and 'may be due to the presence of scattered radiation'; agreement with Ladenburg and Van Voorhis \(ladenburg\_1933\) in the maximum and its position; below them, and with Schneider, at 60000\-65000 cm^\-1\. Later photoelectric work \(metzger\_1964\: 402 \+\- 20 cm^\-1 at 1422 A\) supports the lower maximum; these photographic values are about 20 % higher near the peak\. Figure 3 \(Beer's law plots at 1435 and 1670 A\) is a figure only\. The band oscillator strengths of the Schumann\-Runge system are part II \(ditchburn\_1954\)\. **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\_1953/means ~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "means", "material": "O2", "file": "O2/ditchburn_1953__means.csv", "table": "tbl_9b71613fa0c5", "quantity": "absorption_cross_section", "unit": "Mb", "scale": 0.03696857671, "abscissa_unit": "cm-1", "wavelength_medium": "vacuum", "use": "primary", "uncertainty": { "column": true, "level": "probable error" } } Table 1 columns 4\-6\: the mean wave number and mean alpha \(cm^\-1 at 1 atm, 0 C\) of 21 groups of neighbouring lines \(both paths\), the points of Fig\. 4; scale = 1e18 / 2\.705e19 \(the paper's N\) to Mb\. sigma is the printed \+\- \(probable error, 'certainly correct within a factor of 2'; see the record's notes\: the printed errors are about 80 n^\-1/2, not the stated 60 n^\-1/2\)\. The group ending at 63810 cm^\-1 \(printed 64108, 277 \+\- 16\) does not reproduce from its lines \(63919, 291\.8\)\: kept as printed, doubt queued\. Temperature not stated \(room temperature\)\. ditchburn\_1953/long\_path ~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "long_path", "material": "O2", "file": "O2/ditchburn_1953__long_path.csv", "table": "tbl_9b71613fa0c5", "quantity": "absorption_cross_section", "unit": "Mb", "scale": 0.03696857671, "abscissa_unit": "cm-1", "wavelength_medium": "vacuum", "use": "check" } Table 1 column 2\: alpha \(cm^\-1 at 1 atm, 0 C\) on single hydrogen lines with the 205 cm path \(1\-12e\-3 mm Hg\), 15 lines; the number of observations per line \(2\-21\) is kept in the printed column\. scale = 1e18 / 2\.705e19 to Mb\. The same observations make up the means dataset\: a check, not fitted beside it\. Per\-line error by the paper's rule about 60 n^\-1/2 cm^\-1 \(probable error; not printed per line\)\. ditchburn\_1953/short\_path ~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "short_path", "material": "O2", "file": "O2/ditchburn_1953__short_path.csv", "table": "tbl_9b71613fa0c5", "quantity": "absorption_cross_section", "unit": "Mb", "scale": 0.03696857671, "abscissa_unit": "cm-1", "wavelength_medium": "vacuum", "use": "check" } Table 1 column 3\: alpha \(cm^\-1 at 1 atm, 0 C\) on single hydrogen lines with the 0\.043 cm path \(5\-200 mm Hg\), 44 lines; the number of observations per line \(3\-64\) is kept in the printed column\. scale = 1e18 / 2\.705e19 to Mb\. The same observations make up the means dataset\: a check, not fitted beside it\. Where both paths measured a line the values differ by up to 35 % \(63810 cm^\-1\: 307 and 228\), within the stated single\-observation error of about 60 cm^\-1\. ditchburn\_1953/maximum ~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "maximum", "material": "O2", "table": "text", "quantity": "absorption_cross_section", "unit": "cm2", "scale": 1e-17, "abscissa_unit": "cm-1", "wavelength_medium": "vacuum", "use": "check", "uncertainty": { "absolute": 0.1, "level": "not stated" } } 1 inline points in the source record. p\. 67 \(and the abstract, p\. 61\)\: 'The maximum value of alpha is 490 cm^\-1, and the corresponding maximum cross\-section is 1\.81 \+\- 0\.1 x 10^\-17 cm^2 at 69000 cm^\-1 and 1450 A', read from the smooth curve of Fig\. 4 through the means\: a check on the means dataset, not independent\. \+\-0\.1e\-17 as printed \(level not stated\)\. ditchburn\_1953/continuum\_f ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .. code-block:: text { "id": "continuum_f", "material": "O2", "table": "text", "quantity": "oscillator_strength", "abscissa": "label", "use": "check", "uncertainty": { "absolute": 0.02, "level": "not stated" } } 1 inline points in the source record. p\. 70, note added in proof\: the oscillator strength of the Schumann\-Runge continuum, 'Making a reasonable extrapolation of the curve in figure 4, we obtain an f\-value of 0\.215 \+\- 0\.020'; integration range and extrapolation not stated\. Index abscissa\: an integrated strength, not a line\. Compare watanabe\_1953 \(0\.161\), metzger\_1964 \(0\.142\), ladenburg\_1933 \(0\.193\)\. Part II \(ditchburn\_1954\) adds its band sum 0\.044 to this for a total of 0\.259\. A check\. 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.