Sedlacko Tibor, Balog Richard, Lafosse Anne, Stano Michal, Matejcik Stefan, Azria Roger, Illenberger Eugen
Institut für Chemie-Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany.
Phys Chem Chem Phys. 2005 Mar 21;7(6):1277-82. doi: 10.1039/b419104h.
The interaction of low energy (< 20 eV) electrons with a five monolayer (ML) film of formic acid (HCOOH) deposited on a cryogenically cooled monocrystalline Au substrate is studied by electron stimulated desorption (ESD) of negatively charged fragment ions. A comparison with results from gas phase experiments demonstrates the strong effect of the environment for negative ion formation via dissociative electron attachment (DEA). From condensed phase formic acid (FA) a strong H desorption signal from a resonant feature peaking at 9 eV is observed. In the gas phase, the dominant reaction is neutral hydrogen abstraction generating HCOO- within a low energy resonance, peaking at 1.25 eV. ESD studies on the isotopomers HCOOD and DCOOH indicate effective H/D exchange in the precursor ion at 9 eV prior to dissociation. The evolution of the desorption signals in the course of electron irradiation and the features in the thermal desorption spectra (TDS) of the electron irradiated film suggest the formation of CO2 at electron energies above 8 eV.
通过带负电荷的碎片离子的电子激发脱附（ESD）研究了低能（<20 eV）电子与沉积在低温冷却的单晶金衬底上的五单层（ML）甲酸（HCOOH）薄膜的相互作用。与气相实验结果的比较表明了环境对通过解离电子附着（DEA）形成负离子的强烈影响。从凝聚相甲酸（FA）中观察到来自9 eV处共振峰的强烈H脱附信号。在气相中，主要反应是中性氢提取，在1.25 eV处的低能共振内产生HCOO-。对同位素异构体HCOOD和DCOOH的ESD研究表明，在解离之前，前体离子在9 eV处发生了有效的H/D交换。电子辐照过程中脱附信号的演变以及电子辐照薄膜的热脱附谱（TDS）中的特征表明，在电子能量高于8 eV时会形成CO2。
