State‐state transitions for CCl 2 (X 1 A 1 , A 1 B 1 , a 3 B 1 ) radical and collisional quenching of CCl 2 (A 1 B 1 and a 3 B 1 ) by O 2 , N 2 , NO, N 2 O, NH 3 , and various aminated molecules

CCl 2 free radicals were produced by a pulsed dc discharge of CCl 4 in Ar. Ground electronic state CCl 2 (X) radicals were electronically excited to the A 1 B 1 (0,4,0) vibronic state with an Nd:YAG laser pumped dye laser at 541.52 nm. Experimental quenching data of excited CCl 2 (A 1 B 1 and a 3 B 1 ) by O 2 , N 2 , NO, N 2 O, NH 3 , NH(CH 3 ) 2 , NH(C 2 H 5 ) 2 , and N(C 2 H 5 ) 3 molecules were obtained by observing the time‐resolved total fluorescence signal of the excited CCl 2 radical in a cell, which showed a superposition of two exponential decay components under the presence of quencher. The quenching rate constants k A of CCl 2 (A) state and k a of CCl 2 (a) state were derived by analyzing the experimental data according to a proposed three‐level model to deal with the CCl 2 (X 1 A 1 , A 1 B 1 , a 3 B 1 ) system. The formation cross sections of complexes of electronically excited CCl 2 radicals with O 2 , N 2 , NO, N 2 O, NH 3 , and aminated molecules were calculated by means of a collision‐complex model. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 351–356, 2002