Electrostatic Ion Beam Trap Research Articles

Detection of recurrent fluorescence from anthracene using an electrostatic ion beam trap

The recurrent fluorescence of anthracene cations (C14H10+) was investigated using an electrostatic ion beam trap. The photon emission from the excited anthracene cations confined in the trap was observed in the order of milliseconds. The photon yields as a function of the wavelength in the range of 450–860 nm were measured by optical filters and a cooled photomultiplier, which revealed that the observed photon emission is attributed to the D2 → D0 transition of C14H10+. However, the time range of the photon emission is considerably longer than that of the spontaneous emission induced by the D2 → D0 transition (<1 μs). The number of photons emitted by the recurrent fluorescence of C14H10+ as a function of time was calculated using the previously reported theoretical decay rates of C14H10+ by recurrent fluorescence and thermal dissociation. The calculation results justified the time dependence of the measured number of photons over the extended time range. These results demonstrate that we successfully detected recurrent fluorescence photons emitted from excited anthracene cations.

Ion-Ion Interaction Induced Nondispersive Dynamics in an Electrostatic Ion Beam Trap

Ion-Ion Interaction Induced Nondispersive Dynamics in an Electrostatic Ion Beam Trap

Time-dependent dynamics of radio-frequency-bunched ions in an electrostatic ion beam trap.

The dynamics of ions in an electrostatic ion beam trap in the presence of an external time-dependent field is studied with a recently developed particle-in-cell simulation technique. The simulation technique, capable of accounting for space-charge effects, has reproduced all the experimental results on the bunch dynamics in the radio frequency mode. With simulation, the motion of ions is visualized in phase space and it is shown that the ion-ion interaction strongly affects the distribution of ions in phase space in the presence of an rf driving voltage.

Simultaneous electrostatic trapping of merged cation & anion beams.

Simultaneous trapping of merged cation and anion beams in the hybrid electrostatic ion beam trap (HEIBT) opens new opportunities for the study of the interactions of isolated atomic molecular or cluster ions with oppositely charged ionic species. Application of the trapped merged beams requires a detailed understanding of the trapping dynamics and the effect of the Coulombic attractive and repulsive forces between the ions on their motion in the trap. The simultaneous trapping regime is explored experimentally for SF6- anion and SF5+ cation beams and compared to realistic ion trajectory simulations. The respective stability of the simultaneously trapped cation and anion beams is experimentally tracked by nondestructive and mass sensitive image charge monitoring. An approximate analytical potential model is presented for modeling the dynamics of trapped ions, providing insight into the role of ion-ion interactions, and suggesting a simplified mirror design.

Thermometry of stored molecular ion beams

The radiative cooling of a stored, initially rotationally hot OH^{-} ion beam is probed by photodetachment using an electrostatic ion beam trap combined with an in-trap velocity map imaging spectrometer, providing direct measurement of the time-dependent rotational population. The rotational temperatures are estimated from photodetached electron spectra as a function of time using a Boltzmann distribution model and further verified by a rate law model using known Einstein coefficients. We demonstrate that during the entire cooling time, the rotational population can be well described by a Boltzmann distribution.

Fast algorithm for time decay estimation with applications to electrostatic ion beam traps

The ability of peptide trapping in an electrostatic ion beam trap (EIBT) is used for the measurement of renin substrate lifetime dependence from the pressure. The time decay estimation is traditionally obtained by optimization of nonlinear curve-fitting in the least-squares sense. This paper presents a novel algorithm to address this problem, using a numerical differentiation method as the basis for lifetime estimation. Simulations results show that the proposed method provides results similar to those obtained with the classical approach, but is faster by about two orders of magnitude. An experimental result is detailed, which shows the adequacy of this algorithm for the real-life monitoring of decay measurements, not only for EIBT, but also for other processes such as luminescence where exponential decay is involved.

Particle-in-cell techniques for the study of space charge effects in an electrostatic ion beam trap.

We developed a simulation technique to study the effect of space charge interaction between trapped ions in the electrostatic ion beam trap (EIBT). The importance of space charge is demonstrated in both the dispersive and the self-bunching regime of the ion trap. The simulation results provide an estimate for the space charge effect on the trapping efficiency. They also allow for a better understanding of the enhanced diffusion and the self-bunching effect and provide a better characterization of the EIBT as a mass spectrometer, where peak coalescence is important. The numerical results reproduce all experimental data, demonstrating the critical importance of including space charge effects, even at low ion density, to understand the ion trap dynamics.

TrapREMI: A reaction microscope inside an electrostatic ion beam trap

A new experimental setup has been developed to investigate the reactions of molecular ions and charged clusters with a variety of projectile beams. An Electrostatic Ion Beam Trap (EIBT) stores fast ions at keV energies in an oscillatory motion. By crossing it with a projectile beam, e.g., an IR laser, molecular reactions can be induced. We implemented a Reaction Microscope (REMI) in the field-free region of the EIBT to perform coincidence spectroscopy on the resulting reaction products. In contrast to prior experiments, this unique combination of techniques allows us to measure the 3D momentum-vectors of ions, electrons, and neutrals as reaction products in coincidence. At the same time, the EIBT allows for advanced target preparation techniques, e.g., relaxation of hot molecules during storage times of up to seconds, autoresonance cooling, and recycling of target species, which are difficult to prepare. Otherwise, the TrapREMI setup can be connected to a variety of projectile sources, e.g., atomic gas jets, large-scale radiation facilities, and ultrashort laser pulses, which enable even time-resolved studies. Here, we describe the setup and a first photodissociation experiment on H2 +, which demonstrates the ion-neutral coincidence detection in the TrapREMI.

Direct measurement of recurrent fluorescence emission from naphthalene ions

In this study, the recurrent fluorescence of naphthalene ions was investigated using an electrostatic ion beam trap. The number of photons from the recurrent fluorescence on the ${D}_{2}\ensuremath{\rightarrow}{D}_{0}$ transition was measured as a function of time, after the production of naphthalene ions by electron impact. The emission of photons was observed over a time range of approximately 10 ms. The variation in the number of photons for such a long time range could be explained by conducting simulations using previously reported theoretical rate constants of both the fragmentation and the recurrent fluorescence of vibrationally hot naphthalene ions.

Harmonic height distribution in pickup spectroscopy within electrostatic ion beam traps.

Pickup spectroscopy is a means of determining the abundance, mass, charge, and lifetime of ions oscillating in electrostatic ion beam traps. Here, we present a framework for describing the harmonic height distribution of the Fourier transform of the pickup signal and discuss the importance of the pickup positioning, bunch dynamics, and pickup width on the harmonic height distribution. We demonstrate the methodology using measurements from a newly constructed electrostatic ion beam trap.

Multiple-ion-ejection multi-reflection time-of-flight mass spectrometry for single-reference mass measurements with lapping ion species.

Repeated switching of electric potentials within a single experimental cycle is introduced for a multi-reflection time-of-flight mass spectrometer (also known as an electrostatic ion beam trap) in order to eject different ion species after different storage times. The method is demonstrated with two cluster ions with considerably different mass-to-charge ratios (the A = 624 and 832 isotopologues of Pb3 + and Pb4 +, respectively) for the specific case where the sequential ejections result in an identical number of revolution periods. Thus, the ions' flight lengths are identical, and the resulting time-of-flight values allow single-reference mass determination. The requirements for the switching time window are studied in detail. For the present system and ion pair, the relative mass uncertainty is found to be 3 · 10-7 for short measurements (≈10 min) and 6 · 10-8 for longer ones (≈2 h).

Ion-ion collision-induced evaporative cooling of atomic and molecular ions by autoresonance in an electrostatic ion beam trap

SynopsisA new method for cooling beams of any ion is introduced. The method is autoresonance acceleration of ions inside an Electrostatic Ion Beam Trap. Intrabunch collisions of trapped (molecular) ions transfer energy from the “cold” part of the population of the ion distribution to the “hot” part, which, in turn, evaporates from the bunch. As a result, bunches of ions were cooled from about 45 K to well below 1 K.

Hybrid Electrostatic Ion Beam Trap (HEIBT): design and simulation of ion-ion and ion-neutral low-energy collisions and ion-laser photoreactions

SynopsisA new hybrid electrostatic ion beam trap (HEIBT) is designed and simulated for low-energy ion-ion, ion-neutral merged beam collision studies as well as ion-laser interaction experiments. The HEIBT is made possible by the design of dichroic electrostatic mirrors that reflect or transmit ion beams of different charge and energy. The experimental setup allows fragment imaging detection of the investigated reaction products ejected outside the trap.

Ion beam trap design looks to capture beams of merged cations and anions

Simulations show that proposed hybrid electrostatic ion beam trap would be capable of cold collisions at low relative velocities between reactants.

Hybrid electrostatic ion beam trap (HEIBT): Design and simulation of ion-ion, ion-neutral, and ion-laser interactions.

Using dichroic electrostatic mirrors, which can reflect a fast ion beam while transmitting a counterion beam, allows extending the field of electrostatic ion trapping. We present the design and simulations of a hybrid electrostatic ion beam trap that allows simultaneous trapping of velocity matched cation and anion beams. The possible merged beam ion-ion, ion-neutral, and ion-laser experiments are discussed.

Fluorescence detection as a new diagnostics tool for electrostatic ion beam traps

In the development towards the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS), an optical detection region for the observation of fluorescent light is added to an electrostatic ion beam trap (EIBT). In addition to its use for highly sensitive collinear laser spectroscopy, this fluorescence detection is introduced as a diagnostics tool for the study of the ion dynamics inside an EIBT. First measurements of collision-induced fluorescence in an EIBT demonstrate the technique’s diagnostics power by tracking the evolution of an ion bunch’s temporal width over its storage time inside the ion trap. Thereby, the time-focus point of the ion bunch can be determined and the influence of space-charge effects in the EIBT can be investigated. Good qualitative agreement is obtained between the measured trend of temporal widths and the simulations of the ions’ trajectories in the trap. Particularly, the observation of self-bunching on the ion-bunch structure for many simultaneously stored ions is reproduced.

Radiative lifetime measurements of metastable levels in Kr3+ using electrostatic ion beam trap

The radiative lifetimes of the metastable 4s24p3 2P3/2 and 2P1/2 levels in Kr3+ ions were measured using an electrostatic ion beam trap. The lifetimes were determined by measuring the number of photons emitted during the 2P3/2 → 4S3/2 and 2P1/2 → 4S3/2 forbidden transitions of the stored Kr3+ ions, as a function of the storage time. The obtained lifetime values for the 2P3/2 and 2P1/2 states were 23.3 ± 1.4 and 52.8 ± 3.8 ms, respectively. For the 2P3/2 state, this is the first experimental investigation of the radiative lifetime. Considering the experimental errors, the obtained lifetimes are consistent with the previously reported theoretical predictions for each state and the experimental result for the 2P1/2 state.

Multiple ion capture and separation in an electrostatic storage device

The present study introduces new approaches for the capture/injection and selection of ions with large mass-to-charge (m/q) differences in an electrostatic ion beam trap (EIBT) or multi-reflection time-of-flight (MR-ToF) device. While no m/q-dependent storage criterion exists for devices of this nature, the process of injecting ions into the trap relies on a timed potential switching and is therefore mass-selective to some extent. To partially circumvent this restriction, the approach of sequential capture is presented, where additional ion species are captured while already-stored ones are unaffected by the switching pulses. Specifically, it is possible to perform a full in-trap lift capture pulse while a given, already-stored ion species is reflected in a mirror potential or passes through the lift electrode itself. Additionally, the technique of ion selection by means of transversal ejection from the trap is extended to allow ion species with large m/q differences to be retained. To this end, deflector functions with different frequencies are added with an AND logic and supplied to an in-trap deflector electrode. The combination of both techniques allows the simultaneous storage of size-selected ion species with an m/q ratio surpassing 4 : 1 at the present setup, where the single-pulse lift capture is restricted to a ratio of only 1.9.

Long-Term Monitoring of the Internal Energy Distribution of Isolated Cluster Systems.

A method is presented to monitor the internal energy distribution of cluster anions via delayed electron detachment by pulsed photoexcitation and demonstrated on Co_{4}^{-} in an electrostatic ion beam trap. In a cryogenic operation, we calibrate the detachment delay to internal energy. By laser frequency scans, at room temperature, we reconstruct the time-dependent internal energy distribution of the clusters. The mean energies of ensembles from a cold and a hot ion source both approach thermal equilibrium. Our data yield a radiative emission law and the absorptivity of the cluster for thermal radiation.

A 6He production facility and an electrostatic trap for measurement of the beta–neutrino correlation

A novel experiment has been commissioned at the Weizmann Institute of Science for the study of weak interactions via a high-precision measurement of the beta–neutrinoangular correlation in the radioactive decay of short-lived 6He. The facility consists of a 14 MeV d+t neutron generator to produce atomic 6He, followed by ionization and bunching in an electron beam ion source, and injection into an electrostatic ion beam trap. This ion trap has been designed for efficient detection of the decay products from trapped light ions. The storage time in the trap for different stable ions was found to be in the range of 0.6 to 1.2 s at the chamber pressure of ∼7 × 10−10 mbar. We present the initial test results of the facility, and also demonstrate an important upgrade of an existing method (Stora et al., 2012) for production of light radioactive atoms, viz. 6He, for the precision measurement. The production rate of 6He atoms in the present setup has been estimated to be ∼1.45×10−4 atoms per neutron, and the system efficiency was found to be 4.0 ± 0.6%. An improvement to this setup is also presented for the enhanced production and diffusion of radioactive atoms for future use.