JILA, University of Colorado, Boulder, Colorado 80309, USA.
J Chem Phys. 2011 Jun 21;134(23):234703. doi: 10.1063/1.3591180.
Jet cooled NO molecules are scattered at 45° with respect to the surface normal from a liquid gallium surface at E(inc) from 1.0(3) to 20(6) kcal/mol to probe rotationally and electronically inelastic scattering from a gas-molten metal interface (numbers in parenthesis represent 1σ uncertainty in the corresponding final digits). Scattered populations are detected at 45° by confocal laser induced fluorescence (LIF) on the γ(0-0) and γ(1-1) A(2)Σ ← X(2)Π(Ω) bands, yielding rotational, spin-orbit, and λ-doublet population distributions. Scattering of low speed NO molecules results in Boltzmann distributions with effective temperatures considerably lower than that of the surface, in respectable agreement with the Bowman-Gossage rotational cooling model [J. M. Bowman and J. L. Gossage, Chem. Phys. Lett. 96, 481 (1983)] for desorption from a restricted surface rotor state. Increasing collision energy results in a stronger increase in scattered NO rotational energy than spin-orbit excitation, with an opposite trend noted for changes in surface temperature. The difference between electronic and rotational dynamics is discussed in terms of the possible influence of electron hole pair excitations in the conducting metal. While such electronically non-adiabatic processes can also influence vibrational dynamics, the γ(1-1) band indicates <2.6 × 10(-4) probability for collisional formation of NO(v = 1) at surface temperatures up to 580 K. Average translational to rotational energy transfer is compared from a hard cube model perspective with previous studies of NO scattering from single crystal solid surfaces. Despite a lighter atomic mass (70 amu), the liquid Ga surface is found to promote translational to rotational excitation more efficiently than Ag(111) (108 amu) and nearly as effectively as Au(111) (197 amu). The enhanced propensity for Ga(l) to transform incident translational energy into rotation is discussed in terms of temperature-dependent capillary wave excitation of the gas-liquid metal interface.
从液态镓表面以 45°角散射与表面法线成直角的 NO 分子，入射能 E(inc)为 1.0(3)至 20(6)千卡/摩尔，以探测气相-液态金属界面的转动和电子非弹性散射（括号中的数字表示相应最后一位数字的 1σ 不确定度）。通过共焦激光诱导荧光（LIF）在γ(0-0)和γ(1-1) A(2)Σ ← X(2)Π(Ω)带检测到散射种群，得到转动、自旋轨道和λ双重态种群分布。低速度 NO 分子的散射导致具有远低于表面温度的有效温度的 Boltzmann 分布，与从受限表面转子态解吸的 Bowman-Gossage 转动冷却模型[J. M. Bowman 和 J. L. Gossage，Chem. Phys. Lett. 96，481（1983）]相当一致。随着碰撞能的增加，散射的 NO 转动能比自旋轨道激发增加得更强，而表面温度的变化则呈现相反的趋势。电子和转动动力学之间的差异是根据在导电金属中电子空穴对激发的可能影响来讨论的。虽然这种电子非绝热过程也可以影响振动动力学，但γ(1-1)带表明在高达 580 K 的表面温度下，NO(v=1)的碰撞形成概率<2.6×10(-4)。从硬立方模型的角度比较平均平移到转动能量转移，并与以前对单晶固体表面上的 NO 散射的研究进行比较。尽管原子质量较轻（70amu），但发现液态 Ga 表面比 Ag(111)（108amu）更有效地将入射平移能转化为转动能，并且几乎与 Au(111)（197amu）一样有效。根据气-液金属界面温度相关的毛细波激发，讨论了 Ga(l)将入射平移能转化为转动能的增强倾向。
