chen_2007#

Y.-H. Chen, S. Varma, A. York and H. M. Milchberg, “Single-shot, space- and time-resolved measurement of rotational wavepacket revivals in H2, D2, N2, O2, and N2O”, Opt. Express 15, 11341 (2007)

Source record · Catalogue · Review register

DOI: 10.1364/OE.15.011341

Source kind: measurement

Recorded technique: Single-shot supercontinuum spectral interferometry in a room-temperature gas cell (2.4-7.8 atm): 110-fs, 800-nm pump; xenon supercontinuum probe and reference; the alignment <cos^2 theta> - 1/3 from the probe phase (Eq. (2)), with 1D space resolution; revivals of H2, D2, N2, O2, N2O, their collisional dephasing, and density-matrix simulations with literature Delta alpha (pp. 11343-11356).

Materials in structured entries: D2, H2, N2, N2O, O2

Dataset quantities: dephasing_time, polarizability_anisotropy, rotational_constant

Contents: 9 datasets; 0 formulas.

Curation notes#

Journal pages 11341-11357 = PDF pages 1-17. Identity checked against the first page.

NO ABSOLUTE n2 OR Delta alpha IS MEASURED: the measured quantity is the alignment (scaled by the literature Delta alpha); the Delta alpha values are inputs of the simulations, all cited to [26] = lin_1976 (the pdf text layer prints ‘[26]’ after each, the markdown lost two of them). They are recorded as reproduced (or excluded, D2).

DEFINITIONS (Gaussian, pp. 11343-11344): Eq. (1) n^2(t) = 1 + 4 pi N (Delta alpha <cos^2 theta>_t + alpha_perp); Eq. (2) Delta n(t) = 2 pi N n0^-1 Delta alpha (<cos^2 theta>_t - 1/3); Eq. (3) adds the electronic hyperpolarizability terms |E(t)|^2 (<sin^4 theta> alpha(3)_xxxx + (1/2)<sin^2 2 theta> alpha(3)_xxzz + <cos^4 theta> alpha(3)_zzzz); the isotropic prompt part ‘(1/2)[...]|E(t)|^2 = n2 I(t)’ with <sin^4> = <sin^2 2 theta> = 8/15, <cos^4> = 1/5 (p. 11344). N2 and N2O: ‘the orientational effects ... dominate the isotropic prompt response n2 I in the vicinity of the 110 fs pump pulse’ (p. 11349); for H2 and D2 the prompt n2 I dominates (pp. 11355-11356).

VALUES (text). Delta alpha (cm3): N2 0.93e-24, N2O 2.79e-24 (p. 11349, ‘[26]’), O2 1.14e-24 (p. 11353), D2 1.14e-24 (p. 11355, ‘[26]’), H2 0.30e-24 (p. 11356, ‘[26]’). Lin et al.’s values are N2 9.3, N2O 27.9, O2 11.4, H2 3.02, D2 2.92 (x 1e-25): N2, N2O, O2 and H2 agree (H2 rounded); D2’s 1.14e-24 is Lin’s O2 value, 3.9 times Lin’s D2 and wahlstrand_2015’s 3.0e-25 (TC-292): excluded. Fitted rotational constants: H2 B = 61.8 cm^-1, D2 B = 30.4 cm^-1 (from the omega_2,0 = 3.44e13 s^-1 peak): the B_fit_* datasets (2026-09-26); used B, cited to [26]: N2 2.0 (p. 11349 and p. 11350), O2 1.44 (p. 11353; T = (2cB)^-1 = 11.6 ps), N2O 0.41 (p. 11349) and 0.412 (p. 11354) cm^-1 (inputs, not stored). Dephasing: O2 1/gamma = 23.2 ps at 5.1 atm (Fig. 5), N2O 23.8 ps at 2.4 atm (Fig. 6): the T2_* datasets (2026-09-26); the N2O rate linear in pressure, 1.46 x 10^10 s^-1 atm^-1 (p. 11356, Fig. 9, from four pressures 2.4-6.4 atm shown only in the figure), is not stored (a rate per pressure is not a dephasing time; as a linewidth coefficient it would be gamma/(2 pi) = 2.32 GHz/atm HWHM, an interpretation the paper does not make).

FITTED B (p. 11355; text layer checked). D2: ‘the peak at omega = 3.44 x 10^13 s^-1 is immediately identified as omega_2,0, and allows us to extract the value of B_D2 = 30.4 cm^-1’; omega_2,0 = 12 pi c B, so B = 3.44e13/(12 pi c) = 30.44 cm^-1 (checked). H2: ‘the rotational constant that best fits the Fourier-transformed response is B_H2 = 61.8 cm^-1, in good agreement with previous values [26]’. No uncertainty is stated for either (the stated errors, ~2 % for D2 and ~15 % for H2, are of the extracted phase shift). These are effective constants of the j = 0 -> 2 beat only (omega_2,0 = 6B, centrifugal distortion ignored), from a Fourier transform over a window of ~2.5 T (D2) or ~3 T (H2): coarse. For comparison, teal_1935’s S(0) lines give 6B_eff = 354.5 cm^-1 (H2, B_eff = 59.1) and 178.8 cm^-1 (D2, 29.8): Chen’s values are 4.6 % and 2.0 % higher. FINDING (p. 11355, text layer checked): ‘The spin of the H nucleus is I_N = 1/2, so that even j states are 3 times more populated than odd j states’ reverses the H2 nuclear-spin weights (shelton_1987 Table 2: g_ns = 1 for even J and 3 for odd J; solprop’s degeneracy_even 1, degeneracy_odd 3); whether the simulations of Fig. 8(c) used the printed or the correct weights cannot be told. The D2 statement (even j twice as populated as odd j, p. 11355) agrees with shelton_1987 (2/1).

DEPHASING (pp. 11352-11353). O2: ‘a damping rate of gamma_j,j-2 = gamma = 4.31 x 10^10 s^-1 (or dephasing time 1/gamma = 23.2 ps) was used. The damping rate was obtained from a fit to the declining peak amplitudes in the time sequence data of Fig. 5(a). Since dephasing is dominated by elastic molecular collisions, there should be little j dependence of the rate; hence we put gamma_j,j-2 = gamma’ (p. 11353; the Fig. 5 caption, p. 11352, prints ‘23.2 ps’, its last digit with an unmapped dot glyph in the extraction; the text layer reads 23.2). 1/gamma is the decay time of the rotational coherences rho_j,j-2 (the alignment revivals), a T2 of the pure rotational Raman (S-branch) coherences taken the same for all j. Room temperature; no uncertainty stated.

Recorded bibliographic identity status: VALIDATED_WITH_WARNINGS. This concerns identification of the source; it does not establish the scientific correctness of its contents.