Resonant energy transfer between highly vibrationally excited RbH(RbD) and H2(D2)

Highlights: • Energy transfer between highly vibrationally excited RbH(RbD) and H2(D2) has been investigated. • In RbH (v″ = 18) + H2, Δv = 2 relaxation is about twice as large as Δv = 1. • In RbH (v″ = 21) + H2 and RbD (v″ = 27, 28) + D2, Δv = 8 relaxation plays important role. - Abstract: An experimental study of vibrational relaxation and V–V and V–R energy transfer in RbH-H2 collisions and their isotopic variants has been performed. In RbH (v″ = 17, 18, 21) + H2, single quantum relaxation accounts for only about 30% of the total relaxation out of v″ states, and multiquantum relaxation makes significant contribution. For RbH (v″ = 18), Δv = 2 relaxation is about twice as large as Δv = 1. The significant fraction (24%) of the initial population for RbH (v″ = 21) prepared by overtone pumping, relaxes to much lower vibrational levels (Δv = −8). The time scales is much shorter than the known collisional lifetimes of the intervening vibrational levels and thus a sequential single-quantum relaxation mechanism can be explicitly ruled out. V–V energy transfer is suitable explanation. Energy transfer between RbD (X1Σ+v″ = 21–30) and D2 has been also investigated. V–R and V–V resonance behavior has been also confirmed