Experimental determination of the lowest excited Xe2 molecular states from VUV absorption spectra

A quantitative analysis of absorption by Xe2 pairs in the wings of the two first resonant lines (1469.6 and 1295.6 Å) is presented as a function of pressure (P<760 Torr) and temperature (130 K<T<300 K). Using a quasistatic theory, absorption measurements provide valuable information on the lowest 0u+ and 1u excited states, the 0g+ ground state potential being known from literature. In the near wing region (‖Δν‖<100 cm−1) the shape of the line wings is used as a probe of the asymptotic −2C3/R3−C60/R6 (0u+) and +C3/R3−C61/R6 (1u) potentials assuming at large R a constant oscillator strength, C3 and C6 excited constants are determined. Furthermore the dependence of absorption with temperature is used to derive additional information about the upper states and also to put in evidence some variation of transition moments, at shorter internuclear distances (3.7 Å <R<4.6 Å). The potential curves experimentally derived are compared with ab initio calculated curves.