High-resolution UV spectrum of the benzene-N2 van der Waals complex

The rotationally resolved spectrum of the @ band of the S, + So electronic transition of the benzene-N, van der Waals complex has been recorded and 119 transitions assigned. The G,H,.N, complex, produced in a pulsed molecular beam, was detected by mass-selected two-photon twecolour ionization employing a high-resolution (Av uv = 100 MHz, fwhm) pulsed-amplified cw laser for the resonant intermediate excitation. The observed rotational structure is that of a rigid symmetric top with weaker additional rotational transitions most likely arising from the free internal rotation of the N2 in the plane parallel to the benzene ring. The N2 is located parallel to the benzene ring at a distance of 3.50 A; this decreases by 45 ntA in the excited electronic state. 1