ANALYSIS OF BANDS OF THE 405 nm ELECTRONIC TRANSITION OF C3Ar

Bands of the C3Ar complex can be observed near almost all the bands of the ÃΠu X̃Σg transition of C3. The strongest bands of C3Ar form close-lying pairs. Rotational analyses have been carried out for the bands at 25025 and 25029 cm−1(near the 02−0-000 band of C3) and 25426 and 25430 cm−1(near the 04−0-000 band). Each pair consists of a type A and a type C band of an asymmetric top, where the upper states interact by b-axis Coriolis coupling; this represents the lifting of the degeneracy of the Π state in the lower symmetry of the complex. Only K = even lower state levels are found, showing that C3Ar has the shape of a distorted letter T. The Ar atom lies 3.82 Å from the centre of mass of the C3 part. Emission spectra have been recorded and lifetimes measured for several C3Ar upper state levels. The assignment of the emission bands is complicated by significant intramolecular relaxation in the upper states, which populates mainly the lowest level of each local potential minimum of the upper state; however the variation of the upper state well depth (binding energy) with vibrational quantum number can then be determined.