Highly selective and efficient multiphoton dissociation of polyatomic molecules in multiple-frequency IR-laser fields

An ir multiphoton dissociation (MPD) process in multiple-frequency ir-laser fields has been experimentally realized. A selectivity of S=10⁴ was obtained in separating¹³C/¹²C isotopes upon multiple-frequency ir multiphoton dissociation (MFMPD) of the CF₂HCl molecule, the dissociation yield¹³β for the¹³CF₂HCl molecule amounting to around 1%. A yield of¹³β was reached at a selectivity of S=10², and the total laser fluence required for the process was reduced. A new mechanism-"sticking" of molecules on the lower discrete vibrational levels-responsible for the low MPD yields observed for some molecules is discussed and a technique to eliminate it and thus maximize the dissociation yields is proposed. Ways to improve the selectivity by MFMPD are analyzed and a simple method for obtaining from a single TEA CO₂ laser a multiple-frequency radiation suitable for experimental realization of MFMPD is suggested.