UV emission at 258 nm from the transition of Cl-2(D'-A') was investigated by photoexcitation of the Rydberg states at pressures between 1 and 100 Torr. The intensity of the UV fluorescence produced was increased by a factor of two when the pressure of the buffer gas N-2 was increased from 1 to 20 Torr. Characteristic pressures for quenching and fluorescence enhancement were derived. Kinetic studies revealed the mechanism of the interstate transitions about the generation of the D'-A' transition. A vibrational state redistribution in the excitation spectra for the 2 (1) Sigma(u)(+) state at high pressure was observed. The cause of this is explained in terms of state-dependent quenching.