Experimental and theoretical analysis of the temperature dependence of rotational Raman linewidths of oxygen

This paper is devoted to a detailed study of the self-broadening of rotational Raman lines in oxygen in order to obtain information concerning the anisotropic part of the intermolecular potential using the theory of Smith, Giraud, and Cooper. It first recalls the rotational structure of the energy spectrum of O2 due to its nonzero electronic spin, and shows that a pure Hund’s type b coupling scheme is not adequate. Then the experimental setup and data analysis procedure are discussed in detail to justify the accuracy of the results. In this part the presence of a weak background in addition to Lorentzian Raman lines is discussed but without giving a plausible physical origin. The next part extends the theory of Smith, Giraud, and Cooper to the case of a 3Σ state. The last part presents the experimental results together with theoretical results obtained with an intermolecular potential derived from that of Mingelgrin and Gordon. It is shown that a very good agreement between theory and experiment can be reached provided one takes a slightly steeper repulsive potential. Finally it is shown that the repulsive anisotropic potential is dominating in the whole temperature range that was studied.