State-to-state scattering of highly vibrationally excited NO at broadly tunable energies

Experimental developments continue to challenge the theoretical description of molecular interactions. One key arena in which these advances have taken place is in rotationally inelastic scattering. Electric fields have been used with great success to select the initial quantum state and slow molecules for scattering studies, revealing novel stereodynamics, diffraction oscillations and scattering resonances. These have enjoyed excellent agreement with quantum scattering calculations performed on state-of-the-art coupled-cluster potential energy surfaces. To date these studies have largely employed reactants in the ground vibrational state (v = 0) and the lowest low-field-seeking quantum state. Here we describe the use of stimulated emission pumping to prepare NO molecules in arbitrary single rotational and parity states of v = 10 for inelastic scattering studies. These are employed in a near-copropagating molecular beam geometry that permits the collision energy to be tuned from above room temperature to 1 K or below, with product differential cross-sections obtained by velocity map imaging. This extremely nonequilibrium condition, not found in nature, tests current theoretical methods in a new regime. Scattering experiments in which two beams nearly co-propagate allow broadly tunable collision energies and can enable cold collisions. Now, such experiments have been combined with the preparation of NO molecules using stimulated emission to generate highly vibrationally excited states for state-to-state scattering studies, testing the theoretical gold standard in a regime not found in nature.