Energy transfer of highly vibrationally excited naphthalene: Collisions with CHF3, CF4, and Kr

Energy transfer of highly vibrationally excited naphthalene in the triplet state in collisions with CHF3, CF4, and Kr was studied using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene (2.0 eV vibrational energy) was formed via the rapid intersystem crossing of naphthalene initially excited to the S-2 state by 266 nm photons. The shapes of the collisional energy-transfer probability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. In comparison to Kr atoms, the energy transfer in collisions between CHF3 and naphthalene shows more forward scatterings, larger cross section for vibrational to translational (V -> T) energy transfer, smaller cross section for translational to vibrational and rotational (T -> VR) energy transfer, and more energy transferred from vibration to translation, especially in the range -Delta E-d = -100 to -800 cm(-1). On the other hand, the difference of energy transfer properties between collisional partners Kr and CF4 is small. The enhancement of the V -> T energy transfer in collisions with CHF3 is attributed to the large attractive interaction between naphthalene and CHF3 (1-3 kcal/mol). (C) 2011 American Institute of Physics. [doi:10.1063/1.3622765]