velsko_1986#
S. P. Velsko and D. Eimerl, “Precise measurements of optical dispersion using a new interferometric technique”, Appl. Opt. 25, 1344 (1986)
Source record · Catalogue · Review register
DOI: 10.1364/AO.25.001344
Source kind: measurement
Recorded technique: Nonlinear (second-harmonic) interferometer: a spatially filtered Q-switched Nd:YAG beam at 1.064 um (10 Hz, about 10 mJ) passes two type-II KD*P doublers (3.6 and 4.8 cm) with a gas cell between them (10.41 +- 0.05 cm, or 112.48 +- 0.05 cm for He and Ne); the second-harmonic signal after the second crystal oscillates as the cell pressure is raised (15-100 psia), with period set by n(532 nm) - n(1064 nm) of the gas; I(P) = a + b cos(d + c P l) fitted (Eq. 11). Room temperature 24.5 +- 0.2 degrees C; pressure transducer linear to 1 % (pp. 1344-1347).
Materials in structured entries: None recorded.
Dataset quantities: None recorded.
Contents: 0 datasets; 0 formulas.
Curation notes#
What is measured: the index difference Delta n = n(2 omega) - n(omega) (Eq. 3) between 532 and 1064 nm (vacuum 1.064 um and its harmonic), not n - 1. The format has no quantity for a refractivity difference (nor for Delta k per pressure), so no dataset is recorded; the values are transcribed here from the library tables (tbl_baa16db5a26a, tbl_2379e8dc78c4; the images agree with the CSV cells). A quantity ‘refractivity_difference’ (n(lambda_2) - n(lambda_1) at a state, with parameters.second_wavelength or harmonic = 2) would take Table II; Delta k/N = (4 pi / lambda) Delta n_0 / N_L would put it in phase_mismatch_per_density.
Table I, ‘Coherence lengths of gases, at 1.064 um and 24 degrees C’: the fitted periodicity c in mrad/(psia cm) and l_c (cm) at 1 atm: He 1.591, 268.7; Ne 2.971, 143.9; Ar 29.51, 14.48; Kr 60.50, 7.065; Xe 141.7, 3.017; H2 20.68, 20.67; N2 31.60, 13.53; O2 38.06, 11.23; CO 54.27, 7.876; CO2 66.76, 6.402; CH4 69.6, 6.141; SF6 77.63, 5.506; air 32.65, 13.09. c = 4 pi Delta n_0 (T_0/T)/(lambda P_0) (Eq. 12) with P_0 = 14.696 psia, T_0 = 273.15 K; l_c = lambda/(2 Delta n) (Eq. 7) and indeed l_c = 2 pi/(c x 14.696 psia) for every gas (checked); the text says l_c is ‘at 1 atm and 25 degrees C’, the caption 24 degrees C.
Table II, ‘Dispersion of gases, for 1.064 um and STP’, Delta n_meas x 1e7 (and the authors’ Delta n_calc x 1e7 from Cuthbertson and Cuthbertson’s data in Gmelin, interpolated with a single-pole Sellmeier fit): He 2.160 (3.6), Ne 4.030 (4.7), Ar 40.04 (40.6), Kr 82.05 (79.8), Xe 192.1 (189.5), H2 28.00 (28.6), N2 42.84 (42.9), O2 51.62 (51.2), CO 73.61 (71.6), CO2 90.55 (78.7), CH4 94.40 (none), air 44.29 (44.30, Rankin 1959). SF6 is measured (Table I) but absent from Table II; from c it would be about 105.3e-7 (computed here, not printed). STP means 1 amagat (0 degrees C, 14.696 psia) with pressure proportional to density (‘valid to parts per thousand’ at <= 100 psia): an ideal-gas reduction. Table II agrees with Table I’s c converted at T = 297.65 K to +-0.1 % only (ratios Delta n/c vary from 1.354 to 1.358; checked 2026-09-24), so the two tables are not exact conversions of each other. For helium, puchalski_2016’s series gives Delta alpha = 0.0085939 au between 532 and 1064 nm, i.e. Delta n = 2.150e-7 at the ideal gas at 0 degrees C, 1 atm (computed here), 0.5 % below the measured 2.160e-7, within the stated 2 %.
Accuracy (p. 1347): c ‘varied by < 1 % from run to run’; cell lengths known to better than 0.5 %, transducer linear to 1 %: ‘an overall 95 % confidence interval of 2 % can be quoted for these measurements’. Residual air raises the apparent dispersion of He, Ne and H2 (2 ppt of air adds 5 % to He’s); data were taken while filling, which removes it (Eqs. 13-16). The authors attribute the He discrepancy with Cuthbertson to impurities in Cuthbertson’s helium. Stone and Stejskal (stone_2004) cite Velsko and Eimerl’s helium dispersion as supporting the ab initio helium index. CO (curated since 2026-09-25) is transcribed above with the other gases (Table I 54.27, 7.876; Table II 73.61 against Cuthbertson’s 71.6, 2.8 % apart, beyond the stated 2 %); it gets no dataset, for the same format reason as every gas here. Air is not a curated species. Solids (LiF 0.0069, glass 0.0133) are outside the package.
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 review register for the checks and decisions.