Abstract：Collisional energy transfer processes K2[11Σ+u(v′=2)]+He,H2→K2[11Σ+u(v′=1,3)]+He,H2 were studied by laser induced fluorescence under gas cell conditions. During the experiments, the cell temperature was kept constant at 420K.The buffer gas pressure was varied over the range from 40 to 250 Pa, K2 molecules were irradiated with pulses of radiation from an OPO laser, populating K2[11Σ＋ｕ(v′＝2)] by photon absorption. The resulting fluorescence included the direct component emitted in the decay of the optically excited state and the sensitized components arising from collisionally populated states. The decay signal of time-resolved fluorescence from 11Σ+ｕ(v′＝2)→11Σ+g(v″＝0) transition was monitored. In the early period after excitation, only very little population in states v′＝1 or 3 had yet accumulated, the rate of collisional activation to the state v′＝2 was negligible. The decay curve of the v′＝2→v″＝0 was treated as a single exponential function. From the measurement of the time-resolved fluorescence, the semilog plot was shown. The slope yielded the effective lifetime of the v′＝2→v″＝0 transition. Based on the Stern-Volmer equation, the radiative lifetime (36±7) ns was obtained. The total cross sections for deactivation of 11Σ＋ｕ(v′＝2) state by means of collisions with He and H2 are (3.0±0.5)×10-16 cm2 and (6.4±1.2)×10-15 cm2, respectively.The radiative lifetimes of 11Σ＋ｕ(v′＝1，3) states can also be determined through time-resolved fluorescence in pure K vapor. The time-integrated intensities of 11Σ＋ｕ(v′＝1，2，3)→11Σ＋g(v″＝0) transition at different He or H2 pressure were measured.The ratio of fluorescence intensities versus 1/P(He, H2) can be fitted by a straight line. The slopes yield the cross sections σ(v′＝2→v′＝1)＝(1.4±0.5)×10-16 cm2 and (3.2±1.0)×10-15 cm2; σ(v′＝2→v′＝3)＝(1.2±0.4)×10-16 cm2 and (2.6±0.9)×10-15 cm2 for He and H2, respectively. Cross sections for the effective quenching of the v′＝1，2，3 states were also determined. To our knowledge, the cross-sections for these processes are reported for first time.
Key words：Collisional energy transfer;Time-resolved fluorescence;Time-integrated intensity;Cross-section;K2+He;H2
[1] Flynn G W，Parmenter C S，Wodtke A M. J. Phys. Chem.，1996，100：12817. [2] Yuan L，Du J，Mullin A S. J. Chem. Phys.，2008，129：014303. [3] Barker J R，Yoder L M，King K D. J. Phys. Chem.，2001，A105：796. [4] Oref I，Tardy D C. Chem. Rev.，1990，90：1407. [5] Chen X L，Chen H M，Li J，et al. Chem. Phys. Letters，2000，318：107. [6] Astill A G，Mclaffery A J，Taylor S C，et al. J. Chem. Phys.，1988，89(1)：184. [7] Polly R，Gruder D，Windholz L，et al. Chem. Phys. Letters，1996，249：174. [8] Jarmola A，Tamanis M，Ferber R，et al. J. Quant. Spectro. Rad. Tran.，2005，95：165. [9] Magnier S，Millié Ph. Phys. Rev.，1996，A54(1)：204. [10] WANG Qian，LI Peng，DAI Kang，et al(王 倩，李 鹏，戴 康，等). Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2009，29(9)：2305. [11] Vadla C，Knezovic S，Morre M. J. Phys.，1992，B25：1337.
