A possible use of the radition pressure in a gas for spectroscopic purposes

It is shown that the radiation pressure in the field of oppositely directed quasiresonant optical photon fluxes may produce a very narrow peak (of width less than γ/k) in the atomic velocity distribution function and this may happen in a time of ~10^–6 sec. The position of this peak is governed by the photon detuning. When the detuning is large, the velocity distribution function remains Maxwellian during the cooling of a gas. A potential use of this effect in spectroscopy is discussed.