Abstract We study the excitation redistribution from cesium 7P 1/2 or 7P 3/2 to neighboring energy levels by black body radiation (BBR) and inter atomic collisions using pump-probe spectroscopy inside a vapor cell. At low vapor densities we measure redistribution of the initial, velocity-selected, atomic excitation by BBR. This redistribution preserves the selected atomic velocities allowing us to perform high resolution spectroscopy of the 6D → 7F transitions. This transfer mechanism could also be used to perform sub-Doppler spectroscopy of the cesium highly-excited nG levels. At high densities we observe interatomic collisions redistributing the excitation within the cesium 7P fine and hyperfine structure. We show that 7P redistribution involves state-changing collisions that preserve the initial selection of atomic velocities. These redistribution mechanisms can be of importance for experiments probing high lying excited states in dense alkali vapor.
Abstract We study the excitation redistribution from cesium 7P 1/2 or 7P 3/2 to neighboring energy levels by black body radiation (BBR) and inter atomic collisions using pump-probe spectroscopy inside a vapor cell. At low vapor densities we measure redistribution of the initial, velocity-selected, atomic excitation by BBR. This redistribution preserves the selected atomic velocities allowing us to perform high resolution spectroscopy of the 6D → 7F transitions. This transfer mechanism could also be used to perform sub-Doppler spectroscopy of the cesium highly-excited nG levels. At high densities we observe interatomic collisions redistributing the excitation within the cesium 7P fine and hyperfine structure. We show that 7P redistribution involves state-changing collisions that preserve the initial selection of atomic velocities. These redistribution mechanisms can be of importance for experiments probing high lying excited states in dense alkali vapor.
We study the excitation redistribution from cesium 7P1/2 or 7P3/2 to neighboring energy levels by Black Body Radiation (BBR) and inter atomic collisions using pump-probe spectroscopy inside a vapor cell. At low vapor densities we measure redistribution of the initial, velocity-selected, atomic excitation by BBR. This preserves the selected atomic velocities allowing us to perform high resolution spectroscopy of the 6D→7F transitions. This transfer mechanism could also be used to perform sub-Doppler spectroscopy of the cesium highly-excited nG levels. At high densities we observe interatomic collisions redistributing the excitation within the cesium 7P fine and hyperfine structure. We show that 7P redistribution involves state-changing collisions that preserve the initial selection of atomic velocities. These redistribution mechanisms can be of importance for experiments probing high lying excited states in dense alkali vapor.
We study resonance redistribution mechanisms inside a hot vapor cell. This is achieved by pumping cesium atoms on the 6S 1/2 →6P 1/2 resonance and subsequently probing the velocity distribution of the 6P 1/2 population by a linear absorption experiment on the 6P 1/2 →16S 1/2 or 6P 1/2 →15D 3/2 transitions at 514 nm and 512 nm, respectively. We demonstrate that despite the existence of thermalization processes, traces of the initial velocity selection, imposed by the pump, survive in both hyperfine levels of the intermediate (6P 1/2 ) state. This observation allows us to perform sub-Doppler resolution vapor cell spectroscopy on Rydberg states using a simple pump–probe setup. At high cesium densities, redistribution mechanisms dominate, and the velocity selection vanishes. However, spectral analysis provides the collisional shifts and broadenings of the probed Rydberg states.
Using selective stepwise excitation of the cesium 8S atomic level in Cs vapor, the collisional transfer and the population of the high-lying atomic states were studied in detail. At cesium densities of 10(16)-10(17) cm(-3), the rate coefficient of excitation collision [i. e., 8S+6S --> 6D+6S] was measured. Measurement of fluorescence intensities as a function of Cs density yields k6D = (2.4 +/- 0.5) x 10(-10) cm3 x s(-1). The 5D state was populated by the 8S --> 7P --> 5D transitions. The energy pooling collisions 5D+5D --> nL+6S (nL = 9D, 11S, 7F) were also studied. The rate coefficients were measured relative to the known rate coefficient of the collision [i. e. 6P+5D --> 6S+7D]. The densities of 6P state were combined with measured fluorescence ratios to determine rate coefficients for EP process. The average values (in unites of 10(-10) cm3 x s(-1)) for nL = 9D, 11S and 7F are 6.4 +/- 3.2, 1.0 +/- 0.5 and 8.4 +/- 4.2, respectively.
Using stepwise excitation of the cesium 8S atoms level in Cs vapor,several collisional and radiative processes have been identified from the intensities and spectra of the Cs fluorescence.The 5D state was populated by 8S→7P→5D transitions.In cesium densities 1016-1017?cm-3,the energy pooling collisions 5D+5D→nL+6S(nL=9D,11S,7F are studied.Since the 5D→6P(3.0-3.6 μm) fluorescence could not be detected with this experiment,the EP rate coefficients have been measured relative to the known rate coefficient of the collision,i.e.,6P+5D→6S+7D.The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode laser beam,tuned to 6P3/2→8S1/2 transition,which could be translated parallel to the pump beam.The excited atom densities are combined with measured fluorescene ratios to determine cross sections for the cesium energy pooling process.The average values(in units of 10-10?cm3s-1) for nL=9D,11S and 7F are 8.4±4.2,7.3±3.6,and 9.7±4.8,respectively.Influence on k11S and k7F of the energy transfer process 11S+6S7F+6S is also dicussed.
An experimental study of cesium resonance exchange collision, Cs(6P(3/2), v) + Cs(6S(1/2), v')-->Cs(6S(1/2), v) + Cs (6P(3/2), v'), was carried out. Populations of excited atoms that all have the same z component of velocity were produced by pumping a vapor with a narrow-band laser. A counterpropagating single-mode diode laser was used to probe the excited atom velocity distribution in the 6P(3/2)-->8S(1/2) transition. Fluorescence was monitored in the 8S(1/2)-->6P(3/2) transition. The magnitude of the thermalizinng effect of resonance exchange collisions was estimated by measuring the ratio of the intensity in the narrow features to that associated with the Doppler pedestals. The rate coefficient of 9.62 x 10(-7) cm3 x s(-1) for the resonance exchange collisions was yielded. This work demonstrates that, in a pure metal vapor, the thermalization of velocity-selected excited-atom distribution by the mechanism of resonance exchange can be three orders of magnitude greater than that from velocity-changing collisions.
The method of sensitized fluorescence has been employed to investigate the [Formula: see text] excitation transfer processes in cesium induced in collisions with ground state cesium atoms. The cesium vapor density was kept sufficiently low to enable the cross sections for the mixing process to be determined under single collision conditions and to ensure that radiation trapping and quenching were negligible. A nitrogen laser pumped dye laser was used to excite the cesium atoms to each of the 72P levels in turn and measurements of the relative intensities of fluorescence yielded the following cross sections: [Formula: see text] These results are consistent with the empirical relationship between the magnitude of the cross sections and the fine structure splitting that has previously been determined for the alkalis.