Ion formation upon electron collisions with valine embedded in helium nanodroplets
Ion formation upon electron collisions with valine embedded in helium nanodroplets
复制标题
DOI：
10.1140/epjd/e2016-60737-1
复制
发表时间：
2016-04-19
影响因子：
1.8
通讯作者：
Scheier, Paul
中科院分区：
文献类型：
--
作者：
Weinberger, Nikolaus;Ralser, Stefan;Scheier, Paul
我们在这里报告了大型超流氦纳米液滴的电子电离实验结果，这些液滴的大小约为105个原子，其中掺杂了缬氨酸和缬氨酸簇。采用高分辨率飞行时间质谱法（质量分辨率>4000）监测阳离子和阴离子的光谱。在正离子和阴离子光谱中都可以看到缬氨酸簇大小至少为40且间隔为缬氨酸分子质量的一系列清晰的峰。离子效率曲线为选定的阳离子和阴离子在电子能量高达约40 eV和这些提供洞察离子的形成模式。阳离子的24.59 eV的测量起始值表明了He+对缬氨酸的电离作用，而阴离子形成过程中2,10和22 eV（及以上）的宽共振表明了通过与电子或He*(-)碰撞产生的各种离解电子附着模式的发生，以及液滴大小对这些过程相对重要性的影响。还与气相结果进行了比较，这些结果提供了对超流氦纳米液滴内部基质效应的深入了解。
We report here experimental results for the electron ionization of large superfluid helium nanodroplets with sizes of about 105 atoms that are doped with valine and clusters of valine. Spectra of both cations and anions were monitored with high-resolution time-of-flight mass spectrometry (mass resolution >4000). Clear series of peaks with valine cluster sizes up to at least 40 and spaced by the mass of a valine molecule are visible in both the cation and anion spectra. Ion efficiency curves are presented for selected cations and anions at electron energies up to about 40 eV and these provide insight into the mode of ion formation. The measured onset of 24.59 eV for cations is indicative of valine ionization by He+ whereas broad resonances at 2, 10 and 22 eV (and beyond) in the formation of anions speak to the occurrence of various modes of dissociative electron attachment by collisions with electrons or He*(-) and the influence of droplet size on the relative importance of these processes. Comparisons are also made with gas phase results and these provide insight into a matrix effect within the superfluid helium nanodroplet.