On the combination of a linear field free trap with a time-of-flight mass spectrometer

Abstract

A new instrument has been developed which combines a rf ring electrode trap and a time-of-flight mass spectrometer ͑TOF-MS͒. The wide field free storage volume of such a trap enables the study of low temperature ion-molecule collisions; however it is not straightforward to match the nonlocalized ion cloud to the TOF-MS. For obtaining sufficient mass resolution, a special pulse sequence has been developed to transfer the ions from the whole trap volume to a small region in the vicinity of the exit electrode. Additional compression is achieved via buffer gas relaxation prior to extracting the ions. Using a linear flight path of 57 cm, a mass resolution of about 50 is routinely achieved. The mass range of the whole instrument, which is determined by the operating conditions both of the trap and the TOF-MS, has been estimated to be 3-700 u. The actual characteristics of the instrument such as mass range, resolution, and dynamical range have been determined and the results have been analyzed. As a typical application of the new instrument, the growth of (CO) n ϩ cluster ions is investigated at 80 K. The simultaneous detection of all masses of interest as a function of storage time allows one to follow in detail the kinetics of the reaction and loss processes involved. Limitations of the method are discussed together with ways to overcome them in an improved setup.

The Study of Cold Collisions Using Ion Guides and Traps

“…More work needs to be done in order to optimize the combination of an ion trap with a time of flight mass spectrometer. 66 Low temperatures collisions also could be used successfully in several fields of analytical chemistry. As proposed recently for applications in elemental analysis, 67 the dependence of ternary association on the collision temperature and the number of internal degrees of freedom can be used efficiently for distinguishing between atomic ions and molecular ions with the same mass which otherwise create a background.…”

Trapping ions from a fast beam in a radio-frequency ion trap: Exploring the energy exchange with the longitudinal radio-frequency field

“…11. The design of the ring electrode trap is based on that of Gerlich and co-workers [36]. It consists of a stack of 20 1-mm-thick ring electrodes spaced by 1 mm (2πz 0 = 4 mm) and with an inner radius of r 0 = 5 mm (see Fig.…”

10 K Ring Electrode Trap—Tandem Mass Spectrometer for Infrared Spectroscopy of Mass Selected Ions

“…The RF ring electrode trap is based on the previous design of Gerlich and coworkers. 16 It consists of 24 concentric, 1 mm thick, Molybdenum ring electrodes with a 10 mm inner diameter. The electrodes are electrically isolated from one another by a set of interlocking 1 mm thick sapphire disks, making the entire assembly a gas-tight cylinder.…”

“…This is ideally done using a ringelectrode-trap as originally shown by Gerlich and coworkers. 16 The ring-electrode-trap allows tailoring the electric field along the ion trap axis by superimposing a DC potential gradient on the trapping radio frequency potential. While Gerlich and coworkers used a collinear arrangement of the ion trap and TOF mass spectrometer, we describe an alternative approach here, in which the TOF spectrometer is mounted perpendicularly to the trap axis, allowing for direct optical access along the ion trap axis.…”

“…Coupling a linear RF ion trap to a time-of-flight (TOF) mass spectrometer is more efficient in that it allows to monitor all fragment ion intensities simultaneously, but this adds some additional complexity to the experiment. 16 The ions occupy a large spatial volume in the linear ion trap, while a TOF sampling aperture has a limited spatial extent. In order to achieve high collection efficiencies at the TOF detector the diffuse ion cloud from the trap must be spatially and temporally focused.…”