Resonant rotational energy transfer in HF

Abstract

A molecular beam apparatus has been used to study resonant rotational energy transfer between HF molecules in the ground vibrational state. A low temperature beam formed from the supersonic expansion of a gas mixture containing 1% HF in helium is attenuated by HF molecules with a thermal energy distribution. State selection of the molecular beam is accomplished by using an F-center laser in conjunction with a bolometer detector. The attenuation measurements show effects which are attributed to resonant rotational energy transfer. The results have been analyzed using a kinetic model to estimate the relevant cross sections. The first order dipole allowed process HF(J=0)+HF(J=1) →HF(J=1)+HF(J=0) is found to have a cross section of ∼300 Å2. The results also suggest that the second order cross sections, having ΔJ=2, are about 40 Å2.