Excitation spectra of HgNe and HgAr van der Waals molecules were produ
ced in a pulsed supersonic molecular beam crossed with a pulsed dye-la
ser beam. -Bands arising from A0+ <-- X0+ and B1 <-- X0+ vibronic tran
sitions were analyzed, yielding spectroscopic constants for HgNe and H
gAr. A0+ --> X0+ and B1 --> X0+ fluorescence spectra of HgAr were also
recorded, consisting of Condon internal diffraction patterns arising
from bound-free decays of various vibronic states, together with vibra
tional components produced by bound-bound transitions. Term analyses o
f the spectra combined with computer-modeling calculations produced im
proved values of spectroscopic constants.