Sub-Doppler Spectroscopy of Cs Atoms Optically Pumped in a Thin Cell

Abstract

Optical pumping in a thin Cs vapor cell (end-wall gap 0.5–10 mm) transfers only atoms with small velocity components to a certain energy state. The non-Maxwellian velocity distribution is detected as a hyperfine-resolved spectrum by a double resonance technique using diode lasers. The observed spectral profiles are quantitatively reproduced by the rate-equation analysis in which the velocity-dependent surface relaxation process is taken into account.

On the possibilities of sub-Doppler atomic spectroscopy in multilayer gas cells

“…Meanwhile, obtained qualitative results are valid also for different shapes of a gas cell with spatially separated pumping and probe gas regions, which are connected by plane-parallel thin splits for velocity selection of optically pumped atoms. Moreover, the pumping may be realized also by a resonant narrow-band laser radiation directed even in a transverse direction with respect to the probe light beam as, for example, in experimental works [9][10][11][12][13][14] with a single thin gas cell.…”

“…Later, these methods were successfully realized experimentally for the precision spectral analysis of atoms [7][8][9][10][11][12] and for the laser frequency stabilization [12][13][14][15] on the basis of thin cells (with various inner thicknesses from 10 μm to 10 mm) containing Cs [7][8][9][10][11][13][14][15] or Rb [12] vapors. It is important to note that, unlike the saturated absorption spectroscopy in usual "macroscopic" cells (where L>>D) [1], sub-Doppler spectroscopy in thin gas cells avoids crossover resonances and corresponding stabilization systems are much less affected by frequency fluctuations of the pumping radiation (which may be even broadband) because the velocity selection of optically pumped atoms originates from the cell geometry.…”

“…In particular, the effective spectroscopy method was elaborated with pumping and probe light beams, which may travel through a thin cell even in orthogonal directions [6,[9][10][11][12][13][14]. For example, authors of experimental works [9][10][11][12][13][14] used cylindrical cells (containing Cs or Rb vapor) with the diameter D about 30 mm and different inner thickness L<D from 0.5 mm to 10 mm.…”

“…For example, authors of experimental works [9][10][11][12][13][14] used cylindrical cells (containing Cs or Rb vapor) with the diameter D about 30 mm and different inner thickness L<D from 0.5 mm to 10 mm. In this case the relaxation of pumped long-lived (ground or metastable) atomic levels is caused mainly by collisions of atoms with the end walls of the cell.…”

“…Thus sub-Doppler resonances appear in the absorption spectrum of the probe monochromatic wave (running along the z axis) on central frequencies of optical transitions from given pumped long-lived states to any excited atomic quantum levels. These resonances may be observed directly by the record of the difference between probe signals with and without pumping radiation [9][10][11][12][13][14]. In particular the effective frequency stabilization of a diode laser was achieved on hyperfine components of the Cs 2 D line on the basis of given thin cell spectroscopic methods [13,14].…”