Cluster—Ion Photodissociation and Spectroscopy in a Reflectron Time-of-Flight Mass Spectrometer

Abstract

We describe a configuration for a reflectron time-of-flight mass spectrometer incorporating laser photodissociation of mass--selected ions, and the application of this instrument to studies of metal-containing cluster ions. Metal cluster cations and metal--containing ion-molecule complexes are produced in a molecular beam with a pulsed-nozzle cluster source. We describe here details of the instrument operation for studies of these systems. They exhibit novel cluster photochemistry and vibrationally resolved cluster ion spectroscopy. Advantages and disadvantages of this instrument are discussed.As reflected in this volume, time-of-flight (TOF) spectrometers have many important advantages for modern mass spectrometry. They are ideally suited for experiments employing pulsed laser ionization, ablation, or desorption. The multichannel aspect of mass analysis and ion detection allows rapid data acquisition and processing. It is therefore possible to couple TOF devices to instrument systems requiring fast and repetitive on-line analysis. While TOF systems have historically had poorer resolution than many other mass spectrometers, the introduction of the reflectron time-of-flight (RTOF) design has improved resolution so that it is now acceptable for many applications (1-7). Perhaps the greatest advantage of TOF systems is their high mass range. While most magnetic or electrostatic field instruments are restricted to charge-to-mass ratios of less than 10-20 kDa, TOF instruments now routinely detect species in the range of several hundred kDa. This capability is essential for analysis problems involving high molecular weight polymers, biological molecules, or other novel materials.A serious disadvantage of TOF and RTOF instruments until recently has been the difficulty in utilizing these instruments for tandem mass spectrometry

Photofragmentation of Vanadium Oxide Cations

“…Photofragmentation studies of gas-phase cluster ions can be utilized to provide information on stability, possible structures, and bonding. Photofragmentation techniques have been used to study pure metal, − carbon, , fullerene, , and Met-Car − cluster systems, among many others. To simplify identification of the fragments, typically, a specific cluster is mass selected from a distribution of cluster sizes, prior to photofragmentation.…”

Laser photo-induced dissociation using tandem time-of-flight mass spectrometry

“…Tandem TOF/TOFMS has been previously carried out using a variety of instrument configurations. One easily implemented method involves firing the dissociation laser across the ion path at the back of the reflectron,9–11 where the ions are almost stationary, thus increasing the chance of interaction with the laser beam. The product ions are accelerated and separated in the second part of the reflectron.…”