Fine-structure dependence of the Ar∗ (3P0,2) + N2(X) excitation transfer process Original Research Article

Using diode lasers for the preparation of state selected beams of metastable Ar∗(3P0, 3P2) atoms, the total cross section for the formation of the N2(C,v′) final state has been measured for v′ = 0, 1, 2, and 3, respectively, in a wide range of collision energies 80 < E (meV) < 2000. The energy dependence is very similar for both initial fine structure states and all final vibrational states. The experimental results are described in terms of a coupling of the initial and final state by the intermediate Ar+ + N2− ionic potential, using a Landau Zener model to calculate the transition probability. Due to the similarity in shape, all cross sections are described by a single set of crossing parameters. The observed threshold energy is Ex,i = 63 meV for both fine structure states: the contribution of the 3P0 state does not solve the discrepancy with earlier measurements of other groups. The initial state rotation of the N2 molecules has no influence on the shape of the cross section, as investigated by varying the rotational temperature of the supersonic target beam.