Analysis of the nuclear motion in a HeNe* transient molecule

Based on a model potential for describing the interaction between He and Ne$^{\ast}$ atoms during a collision [1] we predict a series of vibrational states within several electronic adiabatic potential wells of the HeNe$^{\ast }$ system for internuclear distances R $<$ 6 a$_{0}$. The identification of vibrational states suggests the formation of a HeNe$^{\ast }$ temporary molecule. In our study two theoretical approaches are employed: (1) the \textit{harmonic approximation} is based on the assumption that during a collision (which is considered as being one period of vibration) the nuclear motion is harmonic, and (2) the \textit{anharmonic approximation} which uses the best fit of the electronic adiabatic potential wells with a Morse anharmonic function, as is typically done for stable molecules [2]. A set of vibrational-electronic transitions which can be measured using IR spectroscopy is proposed. The relative population of Ne$^{\ast }$ atoms after collisions and successful IR photo-absorption is predicted for experimental testing of the dominant character of the nuclear motion: whether is harmonic or anharmonic. The existence of a HeNe* transient molecule could have a positive impact on improving the performance of He-Ne lasers. [1] Bahrim C, Kucal H and Masnou-Seeuws F 1997 \textit{Phys. Rev. A} \textbf{56} 1305. [2] Bahrim C and Hunt J 2006 \textit{J. Phys. B }\textbf{39} 4683.