Ziemkiewicz Michael, Wojcik Michael, Nesbitt David J
Joint Institute for Laboratory Astrophysics (JILA), National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0040, USA.
J Chem Phys. 2005 Dec 8;123(22):224307. doi: 10.1063/1.2098648.
Quantum-state-resolved reactive-scattering dynamics of F+D(2)O-->DF+OD have been studied at E(c.m.)=5(1) kcal/mol in low-density crossed supersonic jets, exploiting pulsed discharge sources of F atom and laser-induced fluorescence to detect the nascent OD product under single-collision conditions. The product OD is formed exclusively in the v(OD)=0 state with only modest rotational excitation (<E(rot)> =0.50(1) kcal/mol), consistent with the relatively weak coupling of the 18.1(1) kcal/mol reaction exothermicity into "spectator" bond degrees of freedom. The majority of OD products [68(1)%] are found in the ground ((2)Pi(32) (+/-)) spin-orbit state, which adiabatically correlates with reaction over the lowest and only energetically accessible barrier (DeltaE( not equal) approximately 4 kcal/mol). However, 32(1)% of molecules are produced in the excited spin-orbit state ((2)Pi(12) (+/-)), although from a purely adiabatic perspective, this requires passage over a DeltaE( not equal) approximately 25 kcal/mol barrier energetically inaccessible at these collision energies. This provides unambiguous evidence for nonadiabatic surface hopping in F+D(2)O atom abstraction reactions, indicating that reactive-scattering dynamics even in simple atom+polyatom systems is not always isolated on the ground electronic surface. Additionally, the nascent OD rotational states are well fitted by a two-temperature Boltzmann distribution, suggesting correlated branching of the reaction products into the DF(v=2,3) vibrational manifold.
在低密度交叉超声速射流中，于质心能量(E(c.m.) = 5(1))千卡/摩尔条件下，研究了(F + D_2O \to DF + OD)的量子态分辨反应散射动力学，利用(F)原子的脉冲放电源和激光诱导荧光在单碰撞条件下检测初生的(OD)产物。产物(OD)仅在(v(OD) = 0)态形成，只有适度的转动激发（(<E(rot)> = 0.50(1))千卡/摩尔），这与(18.1(1))千卡/摩尔反应放热相对较弱地耦合到“旁观”键自由度一致。发现大多数(OD)产物([68(1)%])处于基态（((^2\Pi_{3/2} (\pm)))）自旋 - 轨道态，该态与越过最低且唯一能量可达的势垒（(\Delta E(\neq))约(4)千卡/摩尔）的反应绝热相关。然而，(32(1)%)的分子产生于激发自旋 - 轨道态（((^2\Pi_{1/2} (\pm)))），尽管从纯绝热角度看，这需要越过在这些碰撞能量下能量不可达的约(25)千卡/摩尔的(\Delta E(\neq))势垒。这为(F + D_2O)原子提取反应中的非绝热表面跳跃提供了明确证据，表明即使在简单的原子 + 多原子系统中，反应散射动力学也并非总是局限于基电子表面。此外，初生(OD)转动态很好地符合双温度玻尔兹曼分布，表明反应产物向(DF(v = 2,3))振动流形的相关分支。
