Infrared Spectra of Rh12C and Rh13C in Solid Neon and Solid Argon

Laser ablated Rh/C alloys produced rhodium and carbon atoms, which react spontaneously to form the RhC molecule in solid argon and neon. Identification of RhC in the matrix IR spectra is supported by carbon-13 substitution and B3LYP density functional frequency calculations. The neon frequency is only 1.6 cm−1 lower than the gas phase fundamental, and the argon matrix red-shift of 15.8 cm−1 is typical for metal species. Geometry optimizations of Ar–RhC complexes gave very long Ar–RhC distances. We suggest weak Van der Waals interactions between RhC and matrix atoms. Although Rh2C and RhC2 species are predicted to be stable, no trace can be found for them in our IR spectra.