Field assessment of sensor technology for environmental monitoring using a process-based soil gas method at geologic CO2 storage sites

Bureau of Economic Geolog

LOW POWER IR PHOTODISSOCIATION OF THE ETHYLENE DIMER

$^{1}$M.A. Hoffbauer, W.R. Gentry and C.F. Giese in Laser-Induced Processes in Molecules, Springer-Verlag Series in Chemical physics, vol. 6, K. Kompa and S. D. Smith, Editors, 1980--in press.Author Institution:The photodissociation band of ethylene dimmer has been measured with low power cw radiation from a $CO_{2}$ laser. In contrast to the pulsed laser $results^{1}$, the band consists of a relatively narrow line, FWHM = $16 cm^{-1}$. More than 60% of the dimer is photodissociated when the P(10) line at $953 cm^{-1}$ interacts with the dimer beam for 340 $\mu$sec with a power density of 18 watts/$cm^{2}$. (The transition is not saturated at the maximum power available.) The power dependence of the photodissociation yield indicates that the one-photon process has a $\sigma = 2 \times 10^{-18}$ $cm^{2}$. The photodissociation yield fits a Lorentzian line profile consistent with a rate of $3 \times 10^{-13}$ sec. No power dependence of the line shape is observed. Analogous results will be presented for $(C_{2}D_{4})_{2}$ and $(NH_{3})_{2}$