The effect of collisions on the resonance fluorescence spectrum of three-level atoms with a V-configuration of levels when excited by two monochromatic resonance fields has been theoretically investigated. The analysis has been carried out for the systems with a small Doppler broadening compared to the collision frequency (high buffer gas pressures) and for the general case of an arbitrary change (from complete failure to complete preservation) of the phase memory at any of the three transitions in the V-system. It has been shown that in the three-level V-type atoms excited by two monochromatic fields, the resonant fluorescence spectrum (the number of spectral lines and their widths) at one of the transitions strongly depends on the presence of resonant radiation at the adjacent transition. Under certain conditions, the line widths will be completely determined by the relaxation characteristics of the adjacent transition and, in particular, can be repeatedly narrowed with an increase in the radiation intensity at the adjacent transition. It has been shown that despite the homogeneous nature of the broadening of the absorption lines, the resonance fluorescence spectrum has a pronounced anisotropy with respect to the mutual orientation of the wave vectors of spontaneous and exciting radiation. It has been established that the line widths in the resonance fluorescence spectrum are proportional to the diffusion coefficient of the atoms interacting with radiation under certain conditions. This fact can serve as the basis for a spectroscopic method for measuring the transport frequencies of the collisions of the radiation-absorbing particles with the buffer ones. It has been shown that the effects of phase memory in the collisions lead to a strong qualitative and quantitative modification of the resonance fluorescence spectrum.
The spectrum of redistributed light that results from excitation by monochromatic near-resonant incident light has been observed in calcium perturbed by argon. The two components were found to be well described by the astrophysical redistribution functions
RII and
RIII for the Rayleigh and fluorescent peaks, respectively. The Doppler width of the Rayleigh component was observed to be \ensuremath{\surd}2 larger than that of the fluorescent component, for our observation at right angle to the incident beam, clearly demonstrating the coherence of this part of the scattering. The ratio of fluorescent to Rayleigh intensity was independent of detuning within our range, which was well within the impact region, and increased linearly with argon pressure in a manner that is consistent with an identification of the cross section for redistributing collisions with that for line broadening.
The variation in the 87Rb D1 (λ = 794.8 nm) pumping light profiles due to 85Rb filter cell temperatures (< 80 °C) has been explained by considering both the shift and broadening of the 85Rb absorption spectrum caused by low-pressure foreign gases (< 200 Torr). The coefficients of the pressure shift and broadening by N2 gas were obtained as −8.0 ± 0.5 and 11 ± 1 MHz/Torr, respectively. The intensity ratio and difference of two peaks in the profiles were calculated in order to discuss the variation in the profiles quantitatively. The foreign gas He was examined for comparison. The absorption coefficient of Rb was also discussed.