Predictions for the observation of KRb spectra under cold conditions

Quantum-mechanical simulations of the excitation spectra of KRb from the lowest vibrational level of the lowest triplet and singlet electronic states have been performed using recently calculated interaction potential curves and corresponding transition dipole moments. The obtained spectra can be used for a comparison with experimental absorption spectra of KRb molecules produced in their vibronic ground state or attached to cold helium droplets. In addition, we compare the semiclassically simulated spectra with absorption measurements in dense K–Rb vapour at high temperatures, which helped us to identify three diffuse bands as 1 3 Σ + –3 3 Π, 1 3 Σ + –4 3 Π and 1 1 Σ + –4 1 Σ + transitions. The first may be observable in an excitation spectrum of KRb dimer formed on cold helium droplets.