High-Resolution Studies of Secondary Emission Spectrum from Resonantly Excited I2 Molecules

The spectrum of secondarily emitted light from iodine vapor excited by a single-mode Ar + ion laser has been measured in the forward scattering geometry with a resolution of 80 MHz. The observed spectrum has been found to consist of sharp and broad components. This result is shown to be reproduced fairly well by a Monte Carlo simulation of the molecular collision. The cross sections for the soft and hard velocity-changing collisions of an I 2 molecule in the excited state have been obtained as 230 A 2 and 80 A 2 , respectively.