title: Mass and collision cross-section determination using a low-vacuum mass spectrometer.
abstract: A simple low-vacuum mass spectrometer (LVMS) operating in the milliTorr pressure range was developed. The instrument resolves masses by time-of-flight measurements and employs a high-gain, fast-response detector that can operate at these pressures. This instrument allows simultaneous determination of mass and collision cross sections of the ions with the bath gas. Here we demonstrate the LVMS's abilities to determine total collision cross sections for the collisions of organic ions with three background gases, He, N(2), and SF(6). As a demonstration of the system capabilities, the unimolecular interconversion of photochemically produced C(7)H(7)(+) to the tropylium ion structure is investigated.
authors.affiliation: Departments of Environmental Sciences and Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Ring
authors.forename: R
authors.initials: R
authors.lastname: Naaman
authors.forename: Y
authors.initials: Y
authors.lastname: Rudich