Rovibrational State Distributions of H2 in Collisional Energy Transfer between NaK (61Σ+) and H2

The electronic to rovibrational energy transfer between the high-lying 6(1)Sigma(+) state of NaK and H-2 was investigated. The 6(1)Sigma(+) state was excited using the optical-optical double resonance technique. Radiative processes were monitored by fluorescence from the 6(1)Sigma(+) state to the ground 1 (1)Sigma(+) state. The CARS (coherent anti-Stokes Raman scattering) spectral technique was used to probe the internal state distribution of collisionally-populated H-2 molecules. The scanned CARS spectra reveal that during E-V, R energy transfer processes H-2 molecules are produced at v=1, 2 and 3 levels. The semilog plot of the time-resolved H-2 (3, 1) CARS intensity was obtained at a pressure of 4 x 10(4) Pa of H-2. The slop yields an effective quenching rate of 8. 09 x 10(5) s(-1). Analogically, for (3, 2), (3, 3) and (3, 5) levels, the quenching rates are 6. 11 x 10(5), 4. 32 x 10(5) and 2. 45 x 10(5) s(-1), respectively. For (3, 1) (3, 2), (3, 3) and (3, 5) levels, the population ratios were obtained from scanned CARS spectral peaks. For (1, 1), (2, 1), (2, 2) and (2,3) levels, from scanned CARS spectral peaks two possible population ratios were yielded. Through shape simulations of time resolved CARS profiles under a kinetic model the actual population ratios were determined. The n(2)/n(1) n(3)/n(1), n(4)/n(1), n(5)/n(1), n(6)/n(1), n(7)/n(1) and n(8)/n(1) are 0. 51, 0. 97, 0. 45, 0. 18, 0. 10, 0.26 and 0. 31, where n(1), n(2), n(3), n(4), n(5), n(6), n(7) and n(8) represent the number densities of H-2 at (3, 1), (2, 1), (1, 1), (3, 3), (2, 3), (2, 2), (3. 2) and (3,5) levels, respectively. The H-2 molecules produced by energy transfer process were populated by 26% at the v=1 level, 21% at v=2 and 53% at v=3. The major vibrational energy [9. 0 +/- 2. 7) x 10(3) cm(-1)] release and the minor rotational energy [(3. 9 +/- 1. 1) x 10(2) cm(-1)] release are shown. Based on the Stern-Volmer equation, the radiative lifetime is (5. 0 +/- 1. 3) ns for the 6(1)Sigma(+) state, the total rate coefficient for deactivation of 6(1)Sigma(+) state by means of collisions with H-2 is (2. 1 +/- 0. 4) x 10(-1) cm(3) . s(-1). From actual population ratios the rate coefficients (in units of 10(-11) cm(3) .s(-1)) for 6(1)Sigma(+)-(1, 1), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3,3) and (3, 5) are 5. 4 +/- 1. 6, 2. 8 +/- 0. 8, 0. 6 +/- 0. 2, 1. 0 +/- 0. 3, 5. 6 +/- 1. 7, 1.4 +/- 0.4, 2. 5 +/- 0. 8 and 1. 7 +/- 0. 5, respectively.