Study on H <sub>3</sub> <sup>+</sup> formation by synchrotron radiation

Abstract

A molecular beam experiment on the formation of H + 3 has been carried out by using tunable vacuum ultraviolet (VUV) synchrotron radiation. Reflectron time-of-flight mass spectrometer is applied to detect the signal of H + . The ioniza- tion energy (IE) of H2 and the appearance energy (AE) of H + are determined to be 15.41 eV and 14.61 eV, respectively, by measurements of photoionization efficiency (PIE) curves. Additionally, two most likely H + formation ways, (H2)2!H 3 + +H and (H2)3!H + +H+H2, are discussed by ab initio calculations at CCSD(T) and MP2 level with aug-cc-pVQZ basis set and compared with the experimental result. The opti- mized geometries of species involved in the dissociative photoionization channels are also determined at MP2/aug-cc-pVQZ level.