Interatomic potential parameters of CdHe van der Waals complex derived from excitation spectrum of the C11(51P1) ← X10+(51S0) vibrational transition

The first time observed excitation spectrum of the C11(51P1) ← X10+(51S0) transition in CdHe van der Waals molecules is reported. Vibrational spectrum in the UV region (2286.0–2296 Å) was excited in a continuous molecular-jet-expansion beam of CdHe seeded in helium using an in-house-built nitrogen-dye laser system. The excitation spectrum exhibits two vibrational components (v′←v″=0)(v′←v″=0) highly broadened by means of unresolved rotational structure and some additional contributions of “hot-bands” componenets (v′←v″=1)(v′←v″=1). The last effect is due to an extremely small separation of the vibrational levels in the ground X10+ state of the CdHe molecule, where v′=0v′=0 vibrational level is separated from v″=0v″=0 by merely 6.0 cm−1. It follows therefore that even in an extremely cold environment (Tv ≈ 10 K) of a jet-expansion beam the population of v″=1v″=1 level is feasible, due to some residual collisions, and hence the v′←v′=1v′←v′=1 transitions are highly probable. The assignment of vibrational bands and numerical analysis of the spectrum was based and obtained with the aid of a rigorous computer simulation of the C11 ← X10+ transition including the impact of rotational structure and hot-bands contributions. As a result we obtained optical potential parameters of the C11(51P1) state of CdHe molecule which are further discussed in terms of our recent (and only existing) experimental results regarding the X10+, B1(53P1) and A0+(53P1) states of CdHe as well as in terms of ab initio calculations results.