Theoretical vibrational and rotational energies and intensities of the HNSi and DNSi molecules

Using the demon density functional program, 104 points on the potential-energy surface for the ground electronic state of the HNSi molecule were calculated. An analytic function was fitted through these points and used in two different computer programs (called Morse oscillator–rigid bender internal dynamics and triatom) to calculate the vibration–rotational energies of the HNSi and DNSi molecules. Other analytic functions were fitted through the calculated dipole-moment data to compute the vibrational transition moments and the vibrationally averaged dipole moments. The computed fundamentals ν1, ν2, and ν3 for HNSi from the triatom program are 3466, 413, and 1172 cm−1, respectively, in reasonable agreement with the observed values of 3588, 523, and 1198 cm−1. Agreement is similar for the Morse oscillator–rigid bender internal dynamics program as well as for DNSi.