The [formula omitted] and [formula omitted] interacting bands of C2D4 by high-resolution FTIR spectroscopy

Abstract

The Fourier transform infrared (FTIR) spectrum of C2D4 in the 1443–1550 cm−1 region was recorded at an unapodized resolution of 0.0063 cm−1 to analyze its A-type ν7+ν8 band. Rovibrational constants of the (ν7=ν8=1) state of C2D4 up to five quartic terms were derived for the first time from a fit 1405 assigned infrared (IR) transitions using the Watson’s A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.00068 cm−1. Majority of the rotational energy levels of the (ν7=ν8=1) state of C2D4 were perturbed by the nearby (ν4=ν8=1) state by a c-type Coriolis interaction. Rovibrational analysis of the IR transitions (both perturbed and unperturbed) of the ν7+ν8 band allows for the c-type Coriolis resonance parameters, Z7,4c and w7,4c, for the ν7+ν8 and ν4+ν8 interacting bands to be determined for the first time. In addition, the band center and three rotational constants (A, B and C) of the unobserved ν4+ν8 band were also derived from the perturbed analysis of this work. The rotational constants of the ν7+ν8 and ν4+ν8 bands derived from this study were found to agree within 2.6% to the calculated values using MP2/cc-pVQZ and B3LYP/cc-pVQZ levels of theory. The band centers of the ν7+ν8 and ν4+ν8 bands were determined to be 1495.894487(40) cm−1 and 1504.5065(37) cm−1 respectively. Furthermore, the band center and rotational constants of the infrared inactive ν8 band of C2D4 were derived from the present analysis of the ν7+ν8 band and that of the previously reported ν7 band of C2D4.