Infrared and Raman Intensities

Infrared intensities can be computed analytically for all HF and DFT wave functions, except for RODFT calculations with an effective core potential. They can also be computed numerically for HF, or DFT wave functions. Infrared intensities for each frequency in km/mol are calculated by default. You do not need to select IR Intensities.1 Keyword irder = 1 in the gen section. For analytic calculations of IR intensities, molecular symmetry is not used. For calculations for which frequencies are computed numerically, the numerical derivative of the dipole moment is used for IR intensity calculations. If you want IR intensities for molecules for which the frequencies would normally be calculated analytically and the IR intensities are not available analytically, the frequencies must be computed numerically, by setting nmder=2 in the gen section.

When frequencies and IR intensities are calculated, a spectrum file is written that contains the spectral data, jobname_vib.spm. This file can be read into the Spectrum Plot Panel in Maestro to generate a simulated ir spectrum. The Spectrum Plot Panel is described in Plotting Spectra.

Raman intensities can be computed for any method that produces vibrational frequencies. The scattering activities and the intensities (including Boltzmann and laser frequency factors [115]) are reported in the output file (see Frequency, IR Intensity, and Thermochemistry Output). A spectrum file is also written with the spectral data for plotting, jobname_raman_vib.spm.

Both IR and Raman intensities are written to the .vib file, which is read by Maestro and used to display frequencies and intensities in the Vibrations Panel (see Animation of Jaguar Frequencies).