Experimental Study of Infrared Multiphoton Absorption of CHClF₂ Molecules

The behavior of multiphoton absorption of CHClF₂ molecule under the irradiation of intense CO₂ laser pulse in the wavelength range from 9.4μm to 10.6μm is reported in this paper. The multiphoton absorption coefficient under both collisionless condition and collision present condition was measured as fuctions of laser frequency, laser energy fluence and gas pressure. Stepwise saturation, superlinear absorption and narrow resonance phenomena were observed. Multiphoton absorption at combination frequency of the molecule was also verified. The EGME incorporating some pressure effects was used to simulate the experimental data on the CHClF₂ excitation in Ar buffer gas. The EGME was numerically solved from trajectory calculations based on a Monte Carlo method. We found that the EGME successfully predicted the IR MPA of CHClF₂ over a wide range of experimental parameters and that the super-linear absorption is mainly owing to the competition of laser excitation and collisional de-excitation