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

The rotationally resolved spectrum of the 610 band of the S1 S0
electronic transition of the benzene—N2 van der Waals complex has
been recorded and 119 transitions assigned. The C6H6·N2 complex,
produced in a pulsed molecular beam, was detected by mass-selected
two-photon two-colour ionization employing a high-resolution (ΔνUV
= 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 Å; this
decreases by 45 mÅ in the excited electronic state.