New simultaneous fit of 12CD4 transitions in the 0–2400 cm−1 region

Abstract

We report the global analysis of 12CD4 line positions from high-resolution rovibrational spectra, including accurate lines in the region 0–2400 cm−1. In addition to the lines of P0–P0 and P1–P1 (where P0 is the ground state (GS), and P1 is the dyad (ν2, ν4)), this region covers two cold polyads: P1 (900–1220 cm−1, two vibrational levels, two sublevels) and the pentad (2ν4, ν2 + ν4, ν1, 2ν2, ν3) or P2 (1850–2400 cm−1, five vibrational levels, nine sublevels). In this analysis, 2724 assignments from four sources are fitted using an effective Hamiltonian expanded up to the sixth 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. Among the 454 parameters of the effective Hamiltonian for the pentad (of which 10 are relative to the GS (or P0) and 72 are relative to the dyad), 233 were fitted (10 of which are GS and 37 of which are dyad). The 47 parameters for the dyad and the 233 parameters for the pentad allow very good simulations to be made. For this study, a total of 2724 line positions were used in the least squares adjustment characterized by the following global root mean square deviations dRMS for line positions: 0.01 × 10−4 cm−1 for P0–P0, 0.4 × 10−4 cm−1 for P1–P1, 1.3 × 10−4 cm−1 for the dyad, and 0.7 × 10−4 cm−1 for the pentad. XTDS and SPVIEW, which can simulate spectra, allowed us to verify and compare the calculated spectrum, to the experimental spectrum for the dyad and pentad regions of 12CD4 and to a spectrum obtained from variational calculation and from ab initio DMS (TheoReTS information system http://theorets.univ-reims.fr or http://theorets.tsu.ru ).