TWO-PHOTON ABSORPTION AS A QUENCHING MECHANISM FOR STIMULATED RAMAN SCATTERING OF $5280 {\AA}$ LASER RADIATION

Author Institution: Electro-Optical Systems IncorporatedThis work was supported in part by the Air Force Avionics Laboratory, Research and Technology Division, Air Force Systems Command, U. S. Air Force. $^{1}$ J. A. Giordmaine and J. A. Howe, Phys. Rev. Letters 11, 207 (1963). $^{2}$ M. El-Sayed, F. M. Johnson and J. A. Duardo, J. Chem, Phys., to be published. $^{3}$ J. A. Duardo and F. M. Johnson, J. Chem, Phys., to be published.Most investigations of stimulated Raman scattering involve the use of giant-pulsed ruby laser radiation $(6943\AA)$. With the exception of $CS_{2}^{1}$ the materials commonly used as scattering samples are free of absorption at wavelengths corresponding to two-photon energies ($\lambda 3470\AA$) of this excitation source. However, when the second harmonic radiation ($\lambda 5300\AA$) of the giant-pulsed neodymium laser is used, two-photon absorption becomes energetically possible for seattering materials such as benzene, and its substituted derivatives, and the alkyl $iodides^{2, 3}$ Theoretical and experimental evidence will be presented which tends to confirm that, for those systems in which the selection rules for two-photon absorption are satisfied, two-photon absorption can occur to such an extent that it completely quenches the SRS process. On the other hand, for some materials which are transparent at $\lambda ^{1}/_{2} (5300\AA)$, e.g., hexane, cyclohexane, acetonitrile, there is evidence that the $5300\AA$ radiation is more efficient than the $6943\AA$ radiation in the production of SRS