Direct measurement of the binding energy of the linear He⋯I35,37Cl(X) isotopomers

Two color, pump–probe action spectra were recorded by tuning an excitation laser through the ICl B–X, 2–0 spectral region and monitoring the fluorescence induced by a probe laser, which was fixed on either the I35Cl or the I37Cl E–B, 13–2 bandhead. A continuum signal is observed above a discrete energy in each of the action spectra that is attributed to bound-free transitions of the He⋯I35,37Cl complexes with preferred linear equilibrium geometries. The shifts of the onsets of the continuum signals from the transition energies of the respective I35Cl and I37Cl B–X, 2–0 band origins correspond to ground state binding energies of 22.3(1.2) and 22.5(1.1) cm−1 for the linear He⋯I35Cl(X,v′′=0) and He⋯I37Cl(X,v′′=0) isotopomers.