Collisional Quenching of Excited Vinylidene (3B2) Radicals

Article abstract of DOI:10.1021/j100412a037

Rate constants for the removal of excited-state vinylidene D2CC (³B₂) in the presence of He, Ar, N2, H2, CO, and CH4 are reported at room temperature.The excited vinylidene radicals are generated via vacuum-ultraviolet photolysis of mixtures of C2D3Cl in the quencher gases through the reeaction sequence C2D3Cl -> C2D3Cl^*; C2D3Cl^* -> D2CC (³B₂) + DCl.Excited triplet vinylidene radicals are then collisionally quenched to the singlet ground state with undergoes rapid isomerization to acetylene.Rate constants for removal of D2CC (³B₂) by quenchers are determined by observation of the time-resolved absorption of either D2CC (³B₂) at 137 nm or product C2D2 at 151 nm.The observed quenching rate constants for the deuterated species are k_He = (1.9 +/- 0.3) * 10^-15, k_Ar = (6.64 +/- 0.3) * 10^-15, k_N2 = (8.5 +/- 0.2) * 10^-15, k_H2 = (33.8 +/- 6.1) * 10^-15, k_CO = (28.0 +/- 8.0) * 10^-15, and k_CH4 = (28.0 +/- 8.0) * 10^-15 cm³ molecule^-1 s^-1.No evidence for chemical reaction could be observed.The derived quenching cross sections are correlated with the potential well depth model.This correlation is valuable in predicting nonreactive collisional cross sections for additional gases.