N. Altstein

Electrostatic ion beam trap for electron collision studies

We describe a system combining an ion beam trap and a low energy electron target in which the interaction between electrons and vibrationally cold molecular ions and clusters can be studied. The entire system uses only electrostatic fields for both trapping and focusing, thus being able to store particles without a mass limit. Preliminary results for the electron impact neutralization of C2− ions and aluminum clusters are presented.

A new type of electrostatic ion trap for storage of fast ion beams

A new technique for trapping of fast (keV) ion beams is presented. The trap, which is electrostatic, works on a principle similar to that of optical resonators. The main advantages of the trap are the possibility to trap fast beams without need of deceleration, the well-defined beam direction, the easy access to the trapped beam by various probes, and the simple requirement in terms of external beam injection. Results of preliminary experiments related to the radiative cooling of molecular ions are also reported.

An innovative approach to multiparticle three-dimensional imaging

An innovative technique for three-dimensional imaging is presented, which uses the ratio of intensities of a pair of two-dimensional images to extract timing information. The principal advantage of this method is the ability to measure position and time for an almost unlimited number of particles hitting the detector simultaneously. The detector is capable of subnanosecond time resolution and position resolution of about 50 mu m. The photodissociation of H-2(+) is used to demonstrate the capability of the detector

Metastable states of negative carbon clusters: Cn−, n=2–6

Time-dependent photodetachment spectra for small electronically and vibrationally excited negatively charged carbon clusters Cn− (n=2–6) are measured using an electrostatic ion trap. The time dependence demonstrates the presence of metastable electronic states with lifetimes in the range of 10 to 200 ms. Comparison is made with available data and theoretical calculations.

Radiative lifetime measurement of the a 3Σ+ metastable state of NO+ using a new type of electrostatic ion trap

A new type of ion trap is used to measure the radiative lifetime of the NO+(a 3Σ+) metastable state. The ion trap is designed to store ion beams with an energy of a few keV and is well suited for the study of metastable states. The measured value for the radiative lifetime is τr=760±30 ms, in good agreement with the last experimental values of Calamai and Yoshino [J. Chem. Phys. 101, 9480 (1994)], and with the theoretical value of Kuo et al. [J. Chem. Phys. 92, 4849 (1990)].

Electrostatic ion beam trap

The conventional way of trapping ions is based on the uses of RF or magnetic fields, like in Paul or Penning traps. In such traps the ions are stored with approximately zero kinetic energy. In many applications a well-defined ion beam is needed especially in collision experiment, where the initial direction of a beam is critical for reaction product measurements and a well defined field free region is required at the collision place. In the last few years we have developed a new type of electrostatic ion trap for ion beams of a few keV per charge, with no mass limit. The ions are injected through a stack of electrodes, which are used as an electrostatic mirror. The ions are confined in a region of few tens of centimeters by two electrostatic mirrors, located on opposite sides. The stability criterion of such a trap can be demonstrated to be similar to the one existing for optical resonator. The dynamics of such trapped ion beam was studied for various potentials on the electrostatic mirrors. Two modes of operation were found. In the first mode a self bunching effect was observed where the ion-ion Coulomb interaction generates a single bunch with constant length along the whole trapping time. This mode of operation can be used for Fourier mass spectrometry. A second mode, where the Coulomb interaction enhances the correlation between the ion position and momentum, enables phase space manipulation of the stored ion beam.