Gas kinetic studies using a table-top set-up with electron beam excitation: quenching of molecular nitrogen emission by water vapour

摘要

A table-top set-up for studying gas kinetic processes in dense gases via time resolved optical spectroscopy is presented. The set-up uses low energy electron beams for gas excitation. A thin silicon nitride membrane separating the electron source and the gas cell allows to use electron energies as low as 10 - 15 keV. The electron source is operated in a fast pulsing mode with a pulse width of 5 ns and repetition rates up to 30 kHz. Light emission from the target gas sample is studied and time resolved photon counting is used to measure decay times and collisional rate constants for specific excited states. The experimental concept is applied to measure the rate constants for quenching of molecular nitrogen in the C (3)&UPi;(u) state ( vibrational levels 0 and 1) by water vapour. Quenching rate constants of ( 7.1 +/- 0.7) x 10(-10) s(-1) cm(3) and (6.7 +/- 0.7) x 10(-10) s(-1) cm(3) were obtained for the C (3)&UPi;(u) ( v = 0) and C (3)&UPi;(u) ( v = 1) vibrational levels, respectively.