Energy-pooling collisions in cesium: 6PJ+6PJ

Abstract

We report experimental rate coefficients for the energy-pooling collisions Cs(6 P 1/2 ) ϩCs(6 P 1/2 )→Cs(6S 1/2 )ϩCs(nl J Ј ) and Cs(6 P 3/2 )ϩCs(6 P 3/2 )→Cs(6S 1/2 )ϩCs(nl J Ј ) where nl J Ј ϭ7P 1/2 , 7 P 3/2 , 6D 3/2 , 6D 5/2 , 8S 1/2 , 4F 5/2 , or 4F 7/2 . Atoms were excited to either the 6 P 1/2 or 6 P 3/2 state using a single-mode Ti:sapphire laser. The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode ring dye laser beam, tuned to either the 6 P 1/2 →8S 1/2 or 6 P 3/2 →7D 3/2,5/2 transitions, which could be translated parallel to the pump beam. Transmission factors, which describe the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed, were calculated for all relevant transitions. Effective lifetimes of levels populated by energy-pooling collisions are modified by radiation trapping, and these factors were calculated using the Molisch theory. These calculated quantities have been combined with the measured excited-atom densities and fluorescence ratios to yield absolute energy-pooling rate coefficients. It was found that the rate for production, in all cases, is greatest for 6D, but that 1/2-1/2 collisions are significantly more efficient than 3/2-3/2 collisions for populating 7 P. It was also found that 7 P 1/2 is populated two to three times more efficiently than 7 P 3/2 in 1/2-1/2 collisions, but that the 7 P fine-structure levels are approximately equally populated in 3/2-3/2 collisions.

Measurement of the self-broadening rate coefficients of the cesium resonance lines

“…From line-center absorption measurements of the cesium D, line hyperfine components, we were able to verify the Nesmeyanov formula at room temperature to within 4.5%, corresponding to a temperature discrepancy of 0.5"C. 24 Since this is equal to the temperature uncertainty, we believe the Nesmeyanov formula is fairly accurate in this low-temperature range. However, as stated above, the extrapolation of this temperature-density relation to the higher temperatures of the present experiment introduces additional uncertainty.…”

Laser energy-pooling processes in an optically thick Cs vapor near a dissipative surface

“…This reaction is a good candidate for the modeling and measurement of the retrofluorescence signal because the reaction has been extensively studied by de Tomasi et al 5 and by Jabbour et al 7 and because the spectral lines at 455.5 and 459.3 nm are easily experimentally observed, as we shall see in Section 4. In formulating our model, we must consider the hyperfine structure of the absorbing Cs transition ͓6 2 S 1/2 → 6 2 P 3/2 ͔. Focusing our attention on reaction (3) allows us to eliminate a number of transitions and levels in Fig.…”

Spectroscopic investigation of sensitized-Cs (62 P3/2–62P1/2) laser retrofluorescence in a pure optically thick vapour near a dissipative surface

“…The work of Jabbour et al [6] indicates that, in Cs vapour resonantly excited at 6 2 P 3/2 , 6 2 D the excited state is predominantly produced during the energy-pooling process (the cross section is at least 10 times larger than the other processes). The reaction 6 2 P + 6 2 P → 6 2 D + 6 2 S in a Cs vapour has been extensively investigated both theoretically and experimentally [4][5][6][7]. The investigation of the 6 2 P 3/2 and 7 2 P 1/2,3/2 levels by retrofluorescence spectroscopy was considered in previous papers [1,2].…”

“…In the case of the selective excitation of one level of the atomic 6 2 P term, the energy-pooling reaction is of the following form: Cs 6 2 P J + Cs 6 2 P J → Cs (nl J ) + Cs 6 2 S 1/2 , where nl J is a highly excited level. The 2Cs 6 2 P 3/2 energy-pooling collisions have been studied extensively both theoretically and experimentally [4][5][6][7][8]: the more efficient reaction is the one that produces the 6 2 D excited state [6]. To our knowledge, no theoretical or experimental spectroscopic works have yet been published describing a thorough study of the population of the 6 2 P 1/2 level at the interface between a dissipative surface and an optically thick Cs vapour, in a regime of selective pumping of 6 2 P 3/2 .…”