T. Mossberg

Optical second-harmonic generation in atomic thallium vapor

Abstract We observe coherent optical second-harmonic generation in atomic thallium vapor when the fundamental is tuned to half the resonance frequency of the following transitions: 6 2 P 1 2 − 7 2 P 3 2 and 6 2 P 1 2 − 8 2 P 3 2 in the presence of a static magnetic field; and 6 2 P 1 2 − 7 2 P 1 2 , 6 2 P 1 2 − 8 2 P 1 2 in the absence of any external field .

Stimulated photon echo study of Na(32S12)-CO velocity-changing collisions

Abstract Using the recently developed single-state stimulated photon echo technique, we have studied the velocity changes experienced by ground-state Na atoms in collisions with carbon monoxide molecules. We find that the ground-state Na atoms have a total cross section of ≈420 A 2 for velocity-changing collisions with CO, and that they experience an average velocity change of ≈600 cm/s. A scattering kernel of exponential form is shown to be consistent with our results. We discuss the essential features of the estimated photon echo technique.

Observation of Dicke superradiance at 1.30 μm in atomic Tl vapor

Abstract Dicke superradiance in the 1.30-μm 7 2 P 1 2 → 7 2 S 1 2 transition in Tl vapor has been induced by a 379.1-nm pulsed dye laser. Superradiant delays of up to 12 nsec have been observed.

Observation and density dependence of the Raman echo in atomic thallium vapor

Abstract Working on the 6P 1 2 −6P 3 2 transition of atomic thallium vapor, we have observed Raman echoes generated by excitation and probe fields detuned from the 7S 1 2 intermediate state by up to 50 cm -1 . This constitutes the first time that echoes, generated by pure two-photon excitation, have been observed in an atomic system. The Raman echo intensity is found to increase roughly as the square of the thallium density at low densities, but at higher densities it peaks and subsequently declines. We suggest that two-photon absorption and loss of phase-matching resulting from excitation-pulse-induced population transfer are important in the high density degradation of the Raman echo signal.

Optical echoes generated by standing-wave fields: Observations in atomic vapors

Abstract We discuss some general features of optical echoes generated in standing-wave (SW) fields. Three types of SW echos - transverse, longitudinal, and stimulated - which we call TSW, LSW and SSW echoes, respectively, are distinguished. We report the first observation of three successive TSW echoes and compare their relative amplitude with theory. We also report the first observation of SSW echoes.

Hyperfine structure of the 72P states of thallium by doppler-free two-photon absorption☆

Abstract Using Doppler-free two-photon absorption, we have measured the hyperfine splittings (hfs) and isotope shifts of the 7 2 P states of natural thallium. We obtain A(7 2 P 3 2 = 310(8) Mhz , and A(7 2 P 1 2 = 2131(60) Mhz . Surprisingly, the 7 2 P 3 2 state hfs is larger than that of the 6 2 P 3 2 state.

Cooperative Effects in Atomic Metal Vapors

In this article we present a summary of some of the preliminary work we have done at Columbia University on the observation of Dicke superradiance in atomic metal vapors. In addition we discuss optical three-wave mixing, a novel effect which is often observed to occur simultaneously with the Dicke superradiance.

Noble Gas Induced Relaxation of the Li 3S-3P Transition Spanning the Short Term Impact Regime to the Long Term Asymptotic Regime

Photon echoes have a Doppler free character which allows one to study relaxation processes which would otherwise be hidden in the inhomogeniously broadened spectral profile. It has recently been shown, for example, that contrary to expection, a radiating atom in a linear superposition of dissimilar electronic states can undergo identifiable velocity changing collisions [1]. Studies of this nature require an examination of the sub-Doppler region of the spectral line shape. The effect manifests itself, in the case of photon echoes, in a dependence of the effective relaxation cross section σeff on the excitation pulse separation τ. In this paper we report measurements in Li vapor where τ can be increased into the regime where σeff once again becomes independent of τ. In the limit τ=0 we measure σ0 which is the phase changing cross section as calculated by Baranger [2] while in the large τ limit we measure σ∞ the average total scattering cross section of the ground and the excited states. Our data at intermediate values of τ is used to determine the form of the scattering kernel and the average velocity change per collision. These measurements are for the 2S–2P superposition states in atomic Li perturbed by each of the noble gases. For He perturbers the scattering kernel is found to be Lorentzian, for the other perturbers it is Gaussian.