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

Abstract The first time observed excitation spectrum of the C 1 1(5 1 P 1 ) ← X 1 0 + (5 1 S 0 ) transition in CdHe van der Waals molecules is reported. Vibrational spectrum in the UV region (2286.0–2296 A) 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 ) highly broadened by means of unresolved rotational structure and some additional contributions of “hot-bands” componenets ( v ′ ← v ″ = 1 ) . The last effect is due to an extremely small separation of the vibrational levels in the ground X 1 0 + state of the CdHe molecule, where v ′ = 0 vibrational level is separated from v ″ = 0 by merely 6.0 cm −1 . It follows therefore that even in an extremely cold environment ( T v  ≈ 10 K) of a jet-expansion beam the population of v ″ = 1 level is feasible, due to some residual collisions, and hence the v ′ ← 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 C 1 1 ← X 1 0 + transition including the impact of rotational structure and hot-bands contributions. As a result we obtained optical potential parameters of the C 1 1(5 1 P 1 ) state of CdHe molecule which are further discussed in terms of our recent (and only existing) experimental results regarding the X 1 0 + , B1(5 3 P 1 ) and A0 + (5 3 P 1 ) states of CdHe as well as in terms of ab initio calculations results.