Mass-Selected Ion-Molecule Cluster Beam Apparatus for Ultrafast Photofragmentation Studies (MICBAUPS)

Electron transfer is an important process in chemistry and biology, where an electron from an anion transfers to a neutral molecule and triggers a dissociation reaction. The electron transfer process has been widely investigated using photoelectron imaging such as velocity mapping imaging in the past twenty years. The detection of fragments including fragment-ions and neutrals is equally important to understand the electron transfer process, especially the dissociation. In this thesis, we will talk about the design and implementation of a novel apparatus to investigate the excited-state dissociation dynamics of mass-selected ion-molecule clusters by mass-resolving and detecting photofragments: fragment ions and neutrals. Here, the dissociation of the ion-molecule cluster in the excited state is triggered by the electron transfer. The apparatus includes the generation of the ion-molecule clusters in a source chamber, separation and selection of the parent ion-molecule cluster using a TOF mass spectrometer and mass filter, and detection of photofragments after laser excitation of ion-molecule clusters using linear-plus-quadratic reflectron mass spectrometer. We have carried out experiments on the CF3I∙I- ion-molecule cluster photoexcited by 266~nm UV femtosecond laser pulses to demonstrate the instrument performance. Anion fragments I- and CF3I- are detected along with neutral fragments. We will compare the experimental results with our electronic structure calculation and the prior work, and discuss the dynamics of the photoexcited cluster