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Optics and Spectroscopy

Effect of collision processes on the decay of population and coherence of the 4/sup 3/D He I state fine-structure levels

S. A. Bagaev, O. V. Oginets, Valerii B Smirnov, V. Yu. Cherepanov

Published Oct 1, 1984• 0 citations
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Collisional alignment of the (3/ital p/)/sup 2//ital P//sub 3/2/ state of sodium during selective excitation of the (3/ital p/)/sup 2//ital P//sub 1/2/ level by monochromatic light

A. G. Petrashen, V. N. Rebane, T. K. Rebane

Calculations of the collisional relaxation of electronic--nuclear polarization moments of all state of the fine and hyperfine structure of the 3/ital p//sup 2//ital P/ doublet of the sodium atom (/ital J/=1/2 and 3/2, nuclear spin /ital I/=3/2) are carried out. The case of selective monochromatic excitation of the fine level /sup 2//ital P//sub 1/2/, allowing for the overlap of the Doppler shapes of the hyperfine components of the spectral line, is discussed. Such excitation gives rise in the /sup 2//ital P//sub 1/2/ state to four groups of excited atoms differing in values of the velocity projection on the direction of the light beam. The problem of collisional relaxation of the polarization moments is solved for each of these groups of atoms, account being taken of the anisotropy of the velocity distribution and intramultiplet mixing. The alignment induced in the levels of the hyperfine structure of the /sup 2//ital P//sub 3/2/ state, populated by anisotropic collisions with atoms of different inert gases, is calculated, as is the linear polarization of the light of sensitized fluorescence. The calculation results are in good agreement with the experiment.

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Collisional Effects in the Saturation Spectroscopy of Three-Level Systems: Theory and Experiment

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Light scattering from laser-trapped atoms

Robert A. Cline, Joseph D. Miller, M. R. Matthews +1 more

We study a novel property of light scattering by Rb atoms confined in a far off-resonance optical dipole force trap. The trapping laser wavelength varies from 780 nm to 860 nm and its intensity is about 1 MW/cm{sup 2}. Spontaneous Raman scattering of photons from the trapping laser can change the ground-state hyperfine quantum number F of the atoms. We observe the relaxation time by measuring the population of the F=3 level after optically pumping the atoms into the F=2 level. Spontaneous photon scatter rates as low as 10{sup 3} s{sup -1} have been observed, corresponding to recoil heating rates below 1 mK/s. For detuning from resonance {Delta} greater than the excited-state fine-structure splitting the total scatter rate, including Rayleigh scattering, decreases as {Delta}{sup 2} while the spontaneous Raman scatter rate decreases as {Delta}{sup 4}. This is due to interference between the Raman scattering amplitudes from the two excited-state fine-structure levels in the Kramers-Heisenberg formula. Because Rayleigh scattering dominates, the atoms` F and M{sub F} quantum numbers are preserved even after many scattering events. This makes far off-resonance optical traps ideal for studies of state-selective collisions and collective phenomena.

Bulletin of the American Physical Society•May 1, 1993•0 citations

COHERENCE RELAXATION OF EXCITED ATOMS IN COLLISIONS

M. I. Dyakonov, V. I. Perel

Журнал Экспериментальной и Теоретической Физики•Jan 1, 1965•2 citations

Measurement of fine-structure changing collision in ultracold /sup 85/Rb held in a MOT

Luís Gustavo Marcassa, R. Zanon, Vanderlei Salvador Bagnato +3 more

Summary form only given. In a magneto-optical trap (MOT) two main mechanisms contribute to the total trap loss rate. Radiative escape (RE), where the spontaneous emission within the collision duration transforms internal energy into kinetic motion. Fine-structure changing collision (FSC) is an exoergic process where a pair of excited ground state atoms undergoes a change to the lower state of the fine-structure doublet, followed by a release of /spl Delta/E/sub FSC//2 in kinetic energy normally enough to eject the atoms from the trap. In earlier experiments only the total trap loss rate, which is the sum of contributions from RE and FSC, was determined. Distinguishing between these two mechanisms is important because it allows a more precise comparison with the theory, leading to a better understanding of exoergic cold collisions. In this experiment the FSC contribution to the total loss in /sup 85/Rb is measured by direct photoionization of the P/sub 1/2/ fragments.

Quantum Electronics and Laser Science Conference•Jan 20, 2003•0 citations
Calculations of the collisional relaxation of electronic--nuclear polarization moments of all state of the fine and hyperfine structure of the 3/ital p//sup 2//ital P/ doublet of the sodium atom (/ital J/=1/2 and 3/2, nuclear spin /ital I/=3/2) are carried out. The case of selective monochromatic excitation of the fine level /sup 2//ital P//sub 1/2/, allowing for the overlap of the Doppler shapes of the hyperfine components of the spectral line, is discussed. Such excitation gives rise in the /sup 2//ital P//sub 1/2/ state to four groups of excited atoms differing in values of the velocity projection on the direction of the light beam. The problem of collisional relaxation of the polarization moments is solved for each of these groups of atoms, account being taken of the anisotropy of the velocity distribution and intramultiplet mixing. The alignment induced in the levels of the hyperfine structure of the /sup 2//ital P//sub 3/2/ state, populated by anisotropic collisions with atoms of different inert gases, is calculated, as is the linear polarization of the light of sensitized fluorescence. The calculation results are in good agreement with the experiment.
We study a novel property of light scattering by Rb atoms confined in a far off-resonance optical dipole force trap. The trapping laser wavelength varies from 780 nm to 860 nm and its intensity is about 1 MW/cm{sup 2}. Spontaneous Raman scattering of photons from the trapping laser can change the ground-state hyperfine quantum number F of the atoms. We observe the relaxation time by measuring the population of the F=3 level after optically pumping the atoms into the F=2 level. Spontaneous photon scatter rates as low as 10{sup 3} s{sup -1} have been observed, corresponding to recoil heating rates below 1 mK/s. For detuning from resonance {Delta} greater than the excited-state fine-structure splitting the total scatter rate, including Rayleigh scattering, decreases as {Delta}{sup 2} while the spontaneous Raman scatter rate decreases as {Delta}{sup 4}. This is due to interference between the Raman scattering amplitudes from the two excited-state fine-structure levels in the Kramers-Heisenberg formula. Because Rayleigh scattering dominates, the atoms` F and M{sub F} quantum numbers are preserved even after many scattering events. This makes far off-resonance optical traps ideal for studies of state-selective collisions and collective phenomena.
Summary form only given. In a magneto-optical trap (MOT) two main mechanisms contribute to the total trap loss rate. Radiative escape (RE), where the spontaneous emission within the collision duration transforms internal energy into kinetic motion. Fine-structure changing collision (FSC) is an exoergic process where a pair of excited ground state atoms undergoes a change to the lower state of the fine-structure doublet, followed by a release of /spl Delta/E/sub FSC//2 in kinetic energy normally enough to eject the atoms from the trap. In earlier experiments only the total trap loss rate, which is the sum of contributions from RE and FSC, was determined. Distinguishing between these two mechanisms is important because it allows a more precise comparison with the theory, leading to a better understanding of exoergic cold collisions. In this experiment the FSC contribution to the total loss in /sup 85/Rb is measured by direct photoionization of the P/sub 1/2/ fragments.