Rotationally inelastic scattering of CD3 and CH3 with He: comparison of velocity map-imaging data with quantum scattering calculations
Rotationally inelastic scattering of CD3 and CH3 with He: comparison of velocity map-imaging data with quantum scattering calculations
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CD3 和 CH3 与 He 的旋转非弹性散射：速度图成像数据与量子散射计算的比较
DOI：
10.1039/c3sc52002a
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发表时间：
2013
期刊：
影响因子：
8.4
通讯作者：
Tkác O
中科院分区：
文献类型：
--
作者：
Tkác O
结合速度图成像实验和量子散射计算，研究了甲基自由基（CD 3和CH 3）与氦碰撞的旋转非弹性散射。在实验中，一束注入Ar的甲基自由基与一束He原子以90°相交，碰撞能量为440 ± 35 cm−1（CD 3 + He）或425 ± 35 cm−1（CH 3 + He）。甲基自由基的制备光解在气体膨胀，冷却到15 K，给一个分布在一个小数目的初始（低）旋转角动量状态。通过共振增强多光子电离探测，我们获得了甲基自由基的单个转动角动量量子数n′的速度图图像，但在投影量子数k′的一个小子集上进行了平均。我们提取了n′ = 2-9（CD 3）的角散射分布。我们比较这些预测的散射计算的基础上进行了最近的势能面[P. J. Dagdigian和M。H.亚历山大，化学物理杂志2011，135，064306]，其中甲基自由基固定在其平衡几何形状。计算得到的（n，k）→（n′，k′）完全分辨的微分截面，当在对应于15 K实验自由基温度的初始（n，k）能级和在光谱探测方案中没有分辨的最终k′能级上进行加权求和时，与所有探测的最终态的实验测量结果非常吻合。这种协议给出了信心的散射的变化在n和k量子数的计算依赖。
Rotationally inelastic scattering of methyl radicals (CD3 and CH3) in collisions with helium is examined by a combination of velocity map imaging experiments and quantum scattering calculations. In the experiments a beam of methyl radicals seeded in Ar intersects a beam of He atoms at 90° at a collision energy of 440 ± 35 cm−1 (CD3 + He) or 425 ± 35 cm−1 (CH3 + He). The methyl radicals are prepared photolytically in a gas expansion that cools them to 15 K, giving a distribution over a small number of initial (low) rotational angular momentum states. By resonance-enhanced multi-photon ionization detection, we obtain velocity map images which are specific to a single rotational angular momentum quantum number n′ of the methyl radicals, but averaged over a small subset of the projection quantum number k′. We extract resolved angular scattering distributions for n′ = 2–9 (for CD3). We compare these to predictions of scattering calculations performed based on a recent potential energy surface [P. J. Dagdigian and M. H. Alexander, J. Chem. Phys. 2011, 135, 064306] in which the methyl radical was fixed at its equilibrium geometry. The fully (n, k) → (n′, k′) resolved differential cross sections obtained from the calculations, when combined in weighted sums over initial (n, k) levels corresponding to the 15 K experimental radical temperature, and final k′ levels that are not resolved in the spectroscopic detection scheme, show excellent agreement with the experimental measurements for all final states probed. This agreement gives confidence in the calculated dependence of the scattering on changes in both the n and k quantum numbers.