Spectroscopy of the A(2)Delta-X-2 Pi transition of CH/D-Ar

The CH(A (2)Delta)-Ar van der Waals molecule provides a prototypical exampl e of a (2)Delta state complex. The rovibronic structure of CH/D(A)-Ar has b een examined by recording rotationally resolved spectra for the A-X transit ion. The spectra are dominated by vibrational progressions of the intermole cular stretch in combination with two bending states. Rotational energy lev el patterns were consistent with a linear equilibrium geometry for CH(A)-Ar . Parity splittings resulting from vibronic interactions were below the res olution of the present measurements. Spectra for the A-X transition of CD, recorded incidentally in this study, reveal an error in the previously acce pted assignment of the 0-0 band R-2(1/2) line. (C) 2000 American Institute of Physics. [S0021-9606(00)01929-2].