Infrared multiple-photon dissociation by an unfocused beam in an optically thick medium: an analytical method for...

Mathematical solutions are derived that, based on the power-law fluence dependence of dissociation probability, describe the reaction yields in infrared multiple-photon dissociation by an unfocused beam in an optically thick medium. Assuming linear absorption (Lambert-Beer's law), we present solutions for both a transversely uniform and a Gaussian beam geometry. An exact solution under a nonlinear absorption condition is also presented for the uniform beam geometry. The critical fluence (?(c)), a characteristic parameter for the dissociation probability, is determined from reaction yields using the solutions. It is found that the value of ?(c) can be fairly accurately determined over a wide range of optical absorption (up to 90% absorption), even when the Lambert-Beer law of absorption is approximately used for analysis instead of the exact treatment of nonlinear absorption.