Line position analysis of the high resolution infrared spectrum of 12CD4 in the region from 900 to 2400 cm−1

Abstract

We report the global analysis of 12CD4 line positions from high-resolution rovibrational spectra, including accurate lines in the region 900–2400cm−1. This covers two cold polyads: the Dyad (ν2, ν4) or P1 (900–1220cm−1, 2 vibrational levels, 2 sublevels) and the Pentad (2ν4, ν2+ν4, ν1, 2ν2, ν3) or P2 (1850–2400cm−1, 5 vibrational levels, 9 sublevels). In this analysis, 2308 data points from three sources are fitted using an effective Hamiltonian expanded up to the fourth order for the Pentad. For the assignments and analysis, we use the SPVIEW and XTDS software programs that implement the tensorial formalism developed in the Dijon group for tetrahedral molecules. Experimental transitions are assigned up to J⩽20 for the Dyad and Pentad cold bands. Among the 206 parameters of the effective Hamiltonian for the Pentad (of which 10 are relative to the Ground State (GS or P0) and 72 are relative to the Dyad), 125 were fitted (8 of which are GS and 40 of which are Dyad). The 48 parameters for the Dyad and the 125 parameters for the Pentad allow very good simulations to be made. For this study, a total of 2308 line positions were used in the least squares adjustment characterized by the following global root mean square deviations dRMS for line positions: 6.2×10−4cm−1 for the Dyad and 3.8×10−4cm−1 for the Pentad. This paper presents a reanalysis of 12CD4 infrared absorption data in order to perform a global fit of line positions for two polyads of this molecule.