Spectroscopic studies of molecular ions and their dissociation dynamics by the threshold photoelectron-photoion coincidence

Abstract

In a recently built threshold photoelectron-photoion coincidence spectrometer, the photoelectrons and photoions were velocity-focused simultaneously to effectively improve the collection efficiency and the energy resolution. With this spectrometer we measured the threshold photoelectron spectra (TPES) and the mass-selected threshold photoelectron-photoion coincidence mass spectra (TPEPICO-MS) of NO molecules, as well as Xe/Ar/Ne rare gas mixtures. The ionization potential of NO was accurately determined, and the vibrationally resolved TPES spectra of the X1Σ+, c3Π and B1Π states of NO+ were obtained. Subsequently, the dissociation dynamics of the c3Π state of NO+ were studied by measuring the TPEPICO-MS and fitting the time-of-flight profile of the N+ fragment. The overall kinetic energy released from dissociation was determined to be 0.717 eV.