Infrared Detection and High-Resolution Spectroscopic Study of Very Heavy Carbon Subchalcogenides: Tricarbon...

Carbon subchalcogenides with tellurium have been studied spectroscopically for the first time in the form of tricarbon telluride, C₃Te, and carbon subtelluride, TeC₃Te. Guided by high-level quantum-chemical calculations performed at the CCSD(T) level of theory using effective-core potentials (to account for scalar-relativistic effects) together with large basis sets, C₃Te and TeC₃Te have been detected at 5 μm wavelengths using high-resolution infrared spectroscopy of laser ablation products from carbon-tellurium targets seeded in a free-jet expansion with a large excess of helium. Because of the rich isotopic composition of tellurium and its high atomic mass, the vibrational bands observed show relatively compact and complex structures, despite the simple linear geometrical arrangements of the carriers. For C₃Te, the spectroscopic pattern found in its ν₁ band enables the identification of five tellurium isotopologues. Owing to an extremely high line density and a poorly resolved spectrum, the analysis of the ν₃ fundamental of TeC₃Te is very complicated, but plausible assignments of the rotational-vibrational structure of the five major isotopic species have been obtained by comparison with results from CCSD(T) calculations.