On the Tunneling Properties of non-Planar Molecules in a Gas Medium
  We propose a simple, general, and accurate formula for analyzing the tunneling between classical configurations of a non-planar molecule in a gas medium, as a function of the thermodynamic parameters of the gas. We apply it to two interesting cases: i) The shift to zero frequency of the inversion line of ammonia, upon increase of the pressure of the gas; ii) The destruction of the coherent tunneling of D2S2 molecules in a gas of He. In both cases, we compare our analysis with previous theoretical and experimental results. 
Mohammad Bahrami, Angelo Bassi
cond-mat.stat-mech quant-ph