Infrared absorption spectroscopy of the CnXe (n = 2, 3, 5, 7, 9) species

Abstract

C_nXe (n = 2, 3, 5, 7, 9) compounds, generated by pulsed laser evaporation of a carbon pellet or by the electrical discharge of acetylene, have been deposited in an argon matrix at 12 K and studied by Fourier transform infrared absorption spectroscopy. Five new vibrational bands at 1774.2, 2033.3, 2161.4, 2126.6 and 1997.2 cm⁻¹ have been observed. Using ab initio MP2 theoretical methods, the first two bands have been assigned to the fundamental stretching modes of C₂Xe and C₃Xe, respectively. These assignments are supported by ¹³C isotopic shift data. The C–Xe bond in C₂Xe is predicted to be stronger than in C₃Xe. Although bent C₃Xe is a little more stable than linear C₃Xe, both species have very flat potential surfaces and both may exist in Ar matrices. The latter three bands are tentatively assigned to C–C asymmetric stretches in C₅Xe, C₇Xe, and C₉Xe, respectively. Despite the lack of isotopic data for these species, this assignment is reasonable based on the smooth frequency shift for the C_nXe species compared to the C_n species.