Sensitive Detection Of Metastable No And N-2 By Reactive Collisions With Laser-Excited Li

In a proof-of-principle experiment, we demonstrate that metastable nitric oxide molecules, NO(a(4)pi(i)), generated inside a pulsed, supersonic beam, can be detected by reactive gas-phase collisions with electronically excited Li atoms in the 2(2)P(3/2) state. Since the internal energy of NO(a(4)pi(i), v <= 4) is lower than the ionization potential of Li in the 2(2)S(1/2) electronic ground state, we observe that the product ion yield arising from autoionizing NO(a(4)pi(i)) + Li(2(2)S(1/2)) collisions is a factor of 21 lower than the ion yield from NO(a(4)pi(i)) + Li(2(2)P(3/2)) collisions. We also compare our findings with measurements of relative rates for metastable N-2 + Li(2(2)S(1/2)) and metastable N-2 + Li(2(2)P(3/2)) reactive collisions. Using this detection method, we infer densities of approximate to 600 NO(a(4)pi(i)) molecules/cm(3) and approximate to 6 . 10(4) metastable N-2 molecules/cm(3) in the interaction region. Our results also allow for an estimate of the fractional population of NO(a(4)pi(i), v > 5) prior to the collision process. The production of NO(a(4)pi(i)) in selected vibrational states using laser excitation from the X-2 pi(r) ground state will open possibilities for the detailed study of vibrational-state-selected NO(a(4)pi(i))-Li(2(2)P(3/2)) collisions.