Kivimäki Antti, Wasowicz Tomasz J, Richter Robert
Nano and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland.
MAX IV Laboratory, Lund University, P.O. Box 118, 22100 Lund, Sweden.
J Phys Chem A. 2021 Jan 28;125(3):713-720. doi: 10.1021/acs.jpca.0c06940. Epub 2021 Jan 12.
Dissociation of water molecules after soft X-ray absorption can yield neutral fragments in high-Rydberg (HR) states. We have studied the production of such fragments by field ionization and ion time-of-flight (TOF) spectrometry. Neutral HR fragments are created at all resonances below the O 1s ionization potential (IP) and particularly within 1 eV above the O 1s IP. The latter effect is due to the recapture of the O 1s photoelectrons into HR orbitals of the molecular water ion after the emission of a fast Auger electron. HO(HR) fragments subsequently dissociate, yielding neutral H(HR) and O(HR) fragments, as were found by measuring the TOF spectra by pulsed field ionization. Such measurements were carried out at the O 1s → 4a and 2b resonances as well as just above the O 1s IP. The TOF spectra also reveal two series of oscillatory structures that are attributed to quantum beats involving Lyman emission in one of the series and field ionization of H(HR) fragments in the other series.
软X射线吸收后水分子的解离可产生处于高里德堡（HR）态的中性碎片。我们通过场致电离和离子飞行时间（TOF）光谱法研究了此类碎片的产生。在低于O 1s电离势（IP）的所有共振处，特别是在高于O 1s IP 1 eV范围内，都会产生中性HR碎片。后一种效应是由于在发射一个快速俄歇电子后，O 1s光电子重新俘获到分子水离子的HR轨道中。通过脉冲场致电离测量TOF光谱发现，HO(HR)碎片随后解离，产生中性H(HR)和O(HR)碎片。此类测量是在O 1s → 4a和2b共振处以及刚好高于O 1s IP处进行的。TOF光谱还揭示了两个系列的振荡结构，其中一个系列归因于涉及莱曼发射的量子拍，另一个系列归因于H(HR)碎片的场致电离。
