Vibrational effects on the polarizability and second hyperpolarizability of ethylene

Static and dynamic polarizabilities and second hyperpolarizabilities are pr esented for ethylene, including electronic, pure vibrational and zero-point vibrational averaging (ZPVA) contributions. Static pure vibrational hyperp olarizabilities are of commensurate size with their electronic counterparts but show less dependence on basis set and(MP2) electron correlation. A Har tree-Fock estimate for the static ZPVA correction to gamma is found to be 1 0% of the corresponding electronic contribution. The dynamic pure vibration al hyperpolarizability, despite being significant for the optical Kerr effe ct and intensity-dependent refractive index, reduces in magnitude for secon d and third harmonic generation, leaving ZPVA as the dominant vibrational e ffect. (C) 1999 Elsevier Science B.V. All rights reserved.