Dynamics of the B ³Π(0u+) and A ³Π(1_u) States of Chlorine by Laser Induced Fluorescence

Abstract

Chlorine B al-I(0+) state lifetimes have been measured by laser-induced fluorescence in several predissociated (v'= 14-19,21) and non-predissociated (v'= 5-12) levels. Trial and error Franck-Condon calculations have been performed to check the nature and position of the predissociating state. The results have been used to give a value of Re for the A aIl(lu) state responsible for predissociation, R 2.48 + 0.01 A. The obtained data show that interference effects due to crossing between B and A states modify the lifetimes of the B state appreciably. The inadequacy of the low-lying vibrational levels region, i.e. v' < 8, to measure the radiative lifetime of the B state (re(B)) is shown. Previous values for re(B) can therefore be affected by considerable errors.

Recombination Reactions of Atomic Chlorine in Compressed Gases. 1. Chemiluminescence Spectra of Chlorine Molecules with Argon Pressure Up to 170 bar

“…Incorporation of the interelectronic coupling to a neighboring electronic state into the above single electronic state mechanism is required to account for the available experimental observations. It has been known that the A and B states of the free chlorine molecules are coupled together through the heterogeneous perturbation interaction. , It is also known that for homonuclear diatomic molecules, such as N 2 , the collisional population transfer within the same spin state is quite efficient if the energy difference between them is within the collisional energy . On the basis of the results of the present study, a natural extension of the above mechanism is the introduction of collisional interelectronic state exchange between B ( v ) and A (μ) if their energy difference is within the thermal energy kT .…”

Comment: “Dynamics of the B and a 3Π(1u) States of Chlorine by Laser Induced Fluorescence”

“…Clearly, at very low pressures, the measured value for the lifetime is limited by the time of free flight to the walls. The cylindrical cell used in reference [1] has a radius of 6 cm, and the free flight to the wall takes typically 200 #s at normal temperature. This limitation is quite severe and explains why the lifetime measurements reported in [1] are all in the range 100-200/s.…”

“…The cylindrical cell used in reference [1] has a radius of 6 cm, and the free flight to the wall takes typically 200 #s at normal temperature. This limitation is quite severe and explains why the lifetime measurements reported in [1] are all in the range 100-200/s. On the contrary, our * also at Universit6 Evry Val d'Essonne ** also at Universit6 Cergy Pontoise 251 experiment 2,3 used a novel technique which we think is better suited to the measurement of long lifetimes.…”

“…Finally, a view is expressed in [1] concerning the A-B mixing. Since the A state is longer lived, this mixing will induce a lengthening of the B state radiative lifetime.…”