[Rovibrational state distributions of H2 in collisional energy transfer between NaK (6(1)sigma(+)) and H2]

The electronic to rovibrational energy transfer between the high-lying 6(1)sigma(+) state of NaK and H2 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 H2 molecules. The scanned CARS spectra reveal that during E-V, R energy transfer processes H2 molecules are produced at v = 1, 2 and 3 levels. The semilog plot of the time-resolved H2 (3, 1) CARS intensity was obtained at a pressure of 4 x 10(4) Pa of H2. 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 n2/n1, n3/n1, n4/n1, n5/n1, n6/n1, n7/n1 and n8/n1 are 0.51, 0.97, 0.45, 0.18, 0.10, 0.26 and 0.31, where n1, n2, n3, n4, n5, n6, n7 and n8 represent the number densities of H2 at (3, 1), (2, 1), (1, 1), (3, 3), (2, 3), (2, 2), (3, 2) and (3, 5) levels, respectively. The H2 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 H2 is (2.1 +/- 0.4) x 10(-10) cm3 x s(-1). From actual population ratios the rate coefficients (in units of 10(-11) cm3 x 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.