The absorption spectrum of nitrosobenzene isolated in solid argon has been studied up to an energy of 45 000 cm(-1). In this medium a previously unreported vibrational structure could be resolved for the first UV band with origin at 30 260 cm(-1). This band is assigned to the S-0 --> S-2 transition. After numerical resolution enhancement with the maximum entropy method this vibrational structure could be analyzed in terms of progressions and combinations of five modes. Line shape analysis of the origin band reveals a superposition of Lorentzian lines with a width of 64 cm(-1), corresponding to a lifetime of the upper electronic state tau(S-2) approximate to 80 fs. The lines are either matrix sites or due to a low-frequency mode. Attempts of spectral hole burning at the electronic origin lead to partial bleaching of the spectrum, which is reversible on a time scale of 20 min. Excitation with an excess energy of 2200 cm(-1) leads to fragmentation into NO and a phenyl radical, which recombine only after annealing of the matrix above 30 K.