hansch_1975

T. W. Hänsch, S. A. Lee, R. Wallenstein and C. Wieman, “Doppler-free two-photon spectroscopy of hydrogen 1S-2S”, Phys. Rev. Lett. 34, 307-309 (1975)

Source record · Catalogue · Review register

DOI: 10.1103/PhysRevLett.34.307

Source kind: measurement

Recorded technique: Doppler-free two-photon excitation of H and D 1S-2S with counter-propagating beams (a retro-reflected standing wave) of a frequency-doubled pulsed dye laser at 2430 Å (fundamental 4860 Å; nitrogen-pumped oscillator and two amplifiers, 10 ns, 30-50 kW in the blue, about 600 W in the ultraviolet after a 1 cm crystal of LiCOOH.H2O (Lasermetrics), bandwidth about 120 MHz in the blue with a confocal filter, 1-2 GHz without; 15 pulses/s; focused to about 0.5 mm), detected by the collision-induced 2P-1S Lyman-alpha fluorescence (solar-blind photomultiplier, 6 % interference filter, signal divided by the square of the ultraviolet intensity). Atoms from a Wood discharge of H2 or D2 (0.1-0.5 Torr). The Balmer-beta absorption profile, recorded with the fundamental in a second discharge, fixes the frequency scale.

Materials in structured entries: None recorded.

Dataset quantities: None recorded.

Contents: 0 datasets; 0 formulas.

Curation notes

Journal pp. 307-309 = PDF pages 1-3 (journal page = PDF page + 306); a scanned PDF with an OCR text layer, the numbers read from the page images. Identity checked on the first page (PDF p. 1: ‘VOLUME 34, NUMBER 6 PHYSICAL REVIEW LETTERS 10 FEBRUARY 1975’, T. W. Hänsch, S. A. Lee, R. Wallenstein and C. Wieman, Stanford, received 23 December 1974) on 2026-10-09. Nothing is taken: the paper prints no level energy and no two-photon strength.

WHAT IS MEASURED (pp. 307-308): the separation of the 1S-2S two-photon resonance from the strongest Balmer-beta component (2P3/2-4D5/2), ‘in terms of the blue-light frequency’, 3.38 +- 0.08 GHz (D) and 3.3 +- 0.2 GHz (H), against the theoretical 3.420 and 3.422 GHz (Garcia and Mack 1965) that omit the 1S Lamb shift; read as the 1S Lamb shift, 8.3 +- 0.3 GHz (D) and 8.6 +- 0.8 GHz (H), against the theoretical 8.172 and 8.149 GHz (the first measurement for H; Herzberg’s 7.9 +- 1.1 GHz for D). The linewidth is the laser’s, about 120 MHz in the blue, under 2 % of the Doppler width; Fig. 3 (p. 309) resolves the F = 1-1 and 0-0 hyperfine components of H at the ultraviolet wavelength labelled ‘2430.7 Å’ (the medium not stated), against the dye laser’s detuning in GHz. NOT TAKEN: the separations and Lamb shifts are frequency intervals that no quantity holds (level_energy holds a level above the ground level, which the paper does not give), and the hyperfine splittings are a declined quantity (TC-1011). Fig. 2 (deuterium) and Fig. 3 are raster spectra with no values.

CALCULATED (p. 309). (a) ‘a two-photon transition rate per atom of Gamma ~ 7 x 10^-4 I^2/Delta omega, where the light intensity I is measured in W/cm2, the laser bandwidth Delta omega in MHz, and Gamma in sec^-1’, from Eq. (7) of Cagnac et al. (1973) with the linewidth replaced by the laser bandwidth, the continuum included. NOT TAKEN: a rate coefficient in mixed units whose profile convention (Delta omega angular or not, in the blue or the ultraviolet, the beams’ geometry) is not stated. It does not reproduce the paper’s own estimate: with the stated 600 W in a 0.5 mm spot (3.06e5 W/cm2), 120 MHz, 10 ns and 1.4e13 atoms/cm3 over 1 cm it gives about 1.5e8 excited atoms per pulse, where the text predicts ‘about 3 x 10^5’, which needs a coefficient near 1.4e-6. The exact per-level sigma_0 = 2.246e-35 cm4 (delta^TP = 246.72 au; quattropani_1982 and drachman_1990), one beam, at the peak of a Lorentzian of FWHM Delta omega in the two-photon angular frequency, gives Gamma = 2.1e-5 I^2/Delta omega (Delta omega in 1e6 rad/s), or 3.4e-6 I^2/Delta nu (Delta nu in MHz): the printed 7e-4 is 33 or 205 times larger (8 or 51 with the factor 4 of a counter-propagating pair), and the text’s 3e5 agrees with the exact strength to a factor 2.5. (b) ‘an intensity shift of about 5.5 Hz/(W/cm2) or less than 2 MHz under the present operating conditions’ of the 1S-2S two-photon resonance (ac Stark effect), by numerically evaluating Eq. (1) of Liao and Bjorkholm (1975). NOT TAKEN under light_shift_coefficient: its sign, which the quantity fixes (positive to the blue), is not stated, nor whether the shift is of the transition or of the laser frequency, nor the intensity’s definition in the standing wave; 2 MHz / 5.5 Hz per W/cm2 = 3.6e5 W/cm2 matches the single-beam 3.06e5 W/cm2 above.

CITED, NOT IN THE LIBRARY: B. Cagnac, G. Grynberg and F. Biraben, J. Phys. (Paris) 34, 845 (1973) (the steady-state two-photon rate, Eq. 7); E. V. Baklanov and V. P. Chebotaev, Opt. Commun. 12, 312 (1974) (the 1S-2S rate without the continuum); P. F. Liao and J. E. Bjorkholm, Phys. Rev. Lett. 34, 1 (1975) (light shifts); and, cited by quattropani_1982 with this paper, S. A. Lee, R. Wallenstein and T. W. Hänsch, Phys. Rev. Lett. 35, 1262 (1975).

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.