Stimulated emission pumping of intermolecular vibrations in OH-Ar(X ²Π)

Stimulated emission spectroscopy has been used to access the intermolecular bending and stretching vibrations supported by the OH(X ²Π) + Ar(¹S₀) potential-energy surfaces. Manifolds of OH-Ar bending levels, correlating with the j = 3/2, 5/2, and 7/2 rotational levels of OH(²Π_3/2), have been observed with zero to three quanta of intermolecular stretch. OH-Ar complexes have also been prepared in intermolecular vibrational levels of the spin-orbit excited state correlating with OH(²Π_1/2). The first dissociation limit, producing OH(²Π_3/2) v = 0, j = 3/2 + Ar(¹S ₀) fragments, has been determined to lie between 93 and 103 cm ^-1 above the zero-point level. Complexes prepared in metastable levels, detected up to 200 cm^-1 beyond the first dissociation limit, undergo predissociation by using OH rotational or spin-orbit excitation to break the OH-Ar intermolecular bond.