Magnetic Bottle Spectrometer Research Articles

Multi-electron–ion coincidence spectrometer with a high-efficiency microchannel plate detector

A microchannel plate detector with a large open area ratio (nominally 90%) has been installed in a magnetic bottle electron spectrometer in order to improve the coincidence efficiency in multi-electron−ion coincidence measurements. The overall detection efficiency of the magnetic bottle spectrometer is determined to be ~70% for electrons with kinetic energies of up to at least 530 eV and ~85% for XeZ+ (Z > 3) ions. The usefulness of the improved detection efficiency in multi-electron−ion coincidence spectroscopy is demonstrated by a six-fold coincidence measurement about the quadruple Auger decay of the Xe 3d5/2 core-hole state.

Core-Level Spectroscopy of 2-Thiouracil at the Sulfur L1- and L2,3-Edges Utilizing a SASE Free-Electron Laser.

In this paper, we report X-ray absorption and core-level electron spectra of the nucleobase derivative 2-thiouracil at the sulfur L1- and L2,3-edges. We used soft X-rays from the free-electron laser FLASH2 for the excitation of isolated molecules and dispersed the outgoing electrons with a magnetic bottle spectrometer. We identified photoelectrons from the 2p core orbital, accompanied by an electron correlation satellite, as well as resonant and non-resonant Coster–Kronig and Auger–Meitner emission at the L1- and L2,3-edges, respectively. We used the electron yield to construct X-ray absorption spectra at the two edges. The experimental data obtained are put in the context of the literature currently available on sulfur core-level and 2-thiouracil spectroscopy.

Magnetic bottle electron spectrometer driven by electron pulses.

We report an electron scattering experiment on argon gas where a keV electron beam is used as a probe and electrons are collected with a magnetic bottle spectrometer. For this purpose, we have built a thermionic gun that produces electron pulses with nanosecond duration by sweeping the beam across a small aperture. To reach the target, electrons must pass through the hole in an axially symmetric arrangement of strong permanent magnets required to operate the magnetic bottle. From the recorded multi-hit sequence of electron arrival times on the microchannel plate detector, a kinetic energy spectrum is built that allows an analysis of the elastic and inelastic electron scattering channels by means of the coincidence technique. After a description of the instrumental configuration and discussion of suitable working parameters, the results of an angle-integrated (e, 2e) experiment are presented for 800 eV electron scattering on argon atoms.

Development of a retarding-field type magnetic bottle spectrometer for studying the internal-conversion process of [formula omitted

The nuclear half-life of 235mU (the first metastable nuclear excited state of235U) varies depending on chemical environments because the nucleus interacts only with outer-shell electrons in the nuclear internal conversion (IC) process due to its extremely low excitation energy at 76.737 ± 0.018 eV. Elucidating the mechanism of the half-life variation of this unique isomer would largely contribute to understanding interactions between nuclei and shell electrons. For elucidating the mechanism, we aim at measuring both half-lives and IC electron energy spectra of 235mU in various chemical environments. In this study, we developed a retarding-field type magnetic bottle spectrometer for measuring the half-lives and energy spectra with high signal to noise ratio (S∕N) and high energy resolution. As an evaluation of the fabricated apparatus, the collection efficiency of electrons emitted from a 235mU sample to a channeltron electron detector was measured as a function of the strong and weak magnetic fields and the collection voltage applied to a mesh placed on the entrance of the channeltron detector. Electron collection efficiencies of almost 100% were confirmed under several conditions. Due to this high efficiency together with the low dark noise of the channeltron detector, high S∕N measurements have been achieved successfully. An IC-electron energy spectrum of 235mU recorded under the most efficient condition showed an energy resolution (ΔE∕E) of ∼2%, which is sufficiently high to observe small peak shifts and splittings in the IC-electron energy spectra of 235mU compounds. This developed apparatus allows high precision measurements of half-lives and IC-electron energy spectra of 235mU in various chemical environments even with small amount of 235mU and low emission rate of IC electrons.

Towards a precise determination of the excitation energy of the Thorium nuclear isomer using a magnetic bottle spectrometer

229Th is the only known nucleus with an excited state that offers the possibility for a direct laser excitation using existing laser technology. Its excitation energy has been measured indirectly to be 7.8(5) eV (≈160 nm). The energy and lifetime of the isomeric state make it the presently only suitable candidate for a nuclear optical clock, the uncertainty of the excitation energy is, however, still too large to allow for a direct laser excitation in a Paul trap. Therefore, a major goal during the past years has been an improved energy determination. One possible approach is to measure the kinetic energy of electrons which are emitted in the internal conversion decay of the first isomeric state in 229Th. For this reason an electron spectrometer based on a magnetic bottle combined with electrical retarding fields has been built. Its design, as well as first test measurements are presented, which reveal a relative energy resolution of 3 % and thus enable to measure the electrons’ expected kinetic energy to better than 0.1 eV. This is sufficiently precise to specify a laser system able to drive the nuclear clock transition in 229Th.

The coincident measurement in the experimental atomic molecular research

The targets of atomic molecular physics are atoms or molecules consist of a few atoms. Due to their simple geometrical structure, in order to obtain unrevealed properties, the advanced experimental techniques are often required to view the target from multi view-points and follow the history of the relevant states if possible. This scientific desire drives us to promote the technical specification and flexibility of instruments. Here, we reviewed several coincident setup, they are based on: field free electron time of flight spectrometer, electron energy-dispersive analyzer, magnetic bottle spectrometer, reaction microscope and velocity map imaging spectrometer. They are widely used in the experiments based on ultrafast laser, free electron laser and synchrotron radiation. We give not only the description of the working principles and the technical differences among them, but also put emphasize on the recent scientific desires and possible breakthroughs.

Construction of a magnetic bottle spectrometer and its application to pulse duration measurement of X-ray laser using a pump-probe method

To characterize the temporal evolution of ultrashort X-ray pulses emitted by laser plasmas using a pump-probe method, a magnetic bottle time-of-flight electron spectrometer is constructed. The design is determined by numerical calculations of a mirror magnetic field and of the electron trajectory in a flight tube. The performance of the spectrometer is characterized by measuring the electron spectra of xenon atoms irradiated with a laser-driven plasma X-ray pulse. In addition, two-color above-threshold ionization (ATI) experiment is conducted for measurement of the X-ray laser pulse duration, in which xenon atoms are simultaneously irradiated with an X-ray laser pump and an IR laser probe. The correlation in the intensity of the sideband spectra of the 4d inner-shell photoelectrons and in the time delay of the two laser pulses yields an X-ray pulse width of 5.7 ps, in good agreement with the value obtained using an X-ray streak camera.

Triple ionization of atomic Cd involving4p−1and4s−1inner-shell holes

The triple ionization spectrum of atomic Cd formed upon the removal of a 4p or a 4s inner-shell electron and subsequent Auger decays has been obtained at 200 eV photon energy. By using a versatile multielectron coincidence detection technique based on a magnetic bottle spectrometer in combination with multiconfiguration Dirac-Fock calculations, Auger cascades leading to tricationic final states have been analyzed and final-state configurations have been identified. The most prominent Auger cascades leading to the ground state of Cd3+ have been identified in good agreement with theory.

Valence Auger decay following3sphotoionization in potassium

We have studied photoionization in the inner valence $3s$ subshell of K and the spectroscopic properties of the two $3{s}^{\ensuremath{-}1}\phantom{\rule{0.28em}{0ex}}(^{1}S)$ and $(^{3}S)$ resulting states. Similar to the Rb and Cs cases, the lifetime widths of the $(^{1}S)$ and $(^{3}S)$ states are found to be markedly different, due to the electron correlation effects. The main part of the study deals with the subsequent Auger decay of the $3{s}^{\ensuremath{-}1}$ states, which have the particularity to involve low energy $(\ensuremath{\sim}5\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$ Auger electrons. A magnetic bottle spectrometer with a multicoincidence technique has been used to observe and filter the Auger spectra with respect to the ${\mathrm{K}}^{2+}$ final state. The evolution of these Auger spectra has been investigated near the ionization threshold. They show strong post-collision interaction (PCI) effects, which are well reproduced by semiclassical and eikonal models. They reveal the importance of the photoelectron--Auger-electron interaction associated with these low energy Auger electrons.

Femtosecond photoelectron and photoion spectrometer with vacuum ultraviolet probe pulses

We describe a femtosecond photoelectron and photoion spectroscopy setup using a simple, novel way to produce a vacuum ultraviolet (VUV) probe pulse. We isolate the femtosecond VUV pulse from a high harmonic continuum by using the bandpass characteristics of a thin indium (In) metal filter. The filter transmits the 9th harmonic of the 800nm laser corresponding to a wavelength of 89nm (hν=14eV). The 9th harmonic is obtained with high conversion efficiencies and has sufficient photon energy to access the complete set of valence electron levels in most molecules. Compared to using grating monochromators, the filter strategy does not change the length of VUV pulse. The setup also allows for direct comparison of VUV single-photon probe with 800nm multi-photon probe without influencing the delay of excitation and probe pulse or the beam geometry. We use a magnetic bottle spectrometer with high collection efficiency for electrons, serving at the same time as a time of flight spectrometer for ions. Characterization measurements on Xe reveal the spectral width of the 9th harmonic to be 190±60meV and a photon flux of ∼1×107photons/pulse after spectral filtering. As a first application, we investigate the S1 excitation of perylene using time-resolved ion spectra obtained with multiphoton probing and time-resolved electron spectra from VUV single-photon probing. The time resolution extracted from cross-correlation measurements is 65±10fs for both probing schemes and the pulse duration of the 9th harmonic is found to be 35±8fs.

A high-resolution magnetic bottle electron spectrometer and its application to a photoelectron–Auger electron coincidence measurement of the L2,3VV Auger decay in CS2

The energy resolution and the detection efficiency of a magnetic bottle electron spectrometer equipped with an electrostatic retarder are examined, with a particular focus on its application to electron coincidence measurements. The electrostatic retardation properly improves the energy resolving power of the spectrometer. No significant decrease in detection efficiency is observed when retardation voltages are applied. Photoelectron–Auger electron coincidence measurement of the L2,3VV Auger decay in CS2 is performed by using the magnetic bottle spectrometer, which reveals Auger transition intensities varying for the different core holes.

Multielectron Spectroscopy: The Xenon4dHole Double Auger Decay

A magnetic bottle spectrometer of the type recently developed by Eland et al. [Phys. Rev. Lett. 90, 053003 (2003).] has been implemented for use with synchrotron radiation, allowing multidimensional electron spectroscopy. Its application to the Xe 4d double Auger decay reveals all the energy pathways involved. The dominant path is a cascade process with a rapid (6 fs) ejection of a first Auger electron followed by the slower (>23 fs) emission of a second Auger electron. Weaker processes implying 3 electron processes are also revealed, namely, direct double Auger and associated Rydberg series.

Above-threshold ionization near the3p4dFo1autoionizing state in magnesium

Two-photon above-threshold ionization (ATI) relative cross sections from the $3\phantom{\rule{0.2em}{0ex}}^{1}P$ state of Mg have been measured using two-color ionization in the focus of a magnetic bottle spectrometer and have been calculated using the Green's-function method in the Feshbach formalism and an ${L}^{2}$-integrable close-coupling approach, with a basis of ${L}^{2}$-integrable $B$-spline functions. We report these cross sections in the region of $3d4p$ $^{1}F^{o}$ autoionizing state, with photon energies of $3.3--3.6\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. This is one of the few direct comparisons between ab initio theory and experiments in ATI in the vicinity of a Feshbach resonance. A good agreement between theory and experiment is found in the relative total cross sections.

Excited state photoelectron spectroscopy on molecular aggregates containing aromatic molecules

Abstract The photoelectron spectra of anisole and its van der Waals aggregates with argon (1:1 and 1:2) or carbon dioxide (1:1) have been measured using resonant two-photon laser ionization and a magnetic bottle spectrometer. The influence of the aggregation toward the intramolecular vibrations is discussed. The evaluation of the photoelectron spectra suggests that two different isomers of the anisole–argon (1:2) aggregate exist in the supersonic beam.

Production of jet-cooled coronene and coronene cluster anions and their study with photoelectron spectroscopy

Anions of coronene (C 24H 12) and its clusters are produced by laser ablation of a pressed pellet sample in a double rod, pulsed nozzle source. Coronene anions are produced efficiently only when transition metal vapor is present in the same plasma from co-vaporization of a metal sample. Anion monomers and clusters of coronene are size-selected and studied with photoelectron spectroscopy in a magnetic bottle spectrometer. Spectra at 532, 355 and 266 nm probe electron affinities and neutral electronic states. The electron affinity of coronene is 0.47±0.09 eV and that of coronene dimer is 0.67±0.09 eV.

Photoelectron spectra of toluene rare gas and toluene diethylether 1:1 complexes

AbstractThe photoelectron spectra of van der Waals dimers of toluene with rare gases or diethylether have been measured using resonant two‐photon laser ionization and a magnetic bottle spectrometer.

Rotational state distributions from vibrational autoionization of H2 revisited

Photoelectron spectra of vibrationally autoionized (X 2Σ+g)np, v=1,2 Rydberg states of H2 were obtained by using an optical–optical double-resonance technique. The spectra were obtained by using a hemispherical electrostatic electron energy analyzer that had sufficient resolution to determine the rotational state distributions of the H+2 ions. The ionization process occurred in a magnetic and electric field-free region. All of the results are consistent with the assumptions that the photoelectrons are ejected as p waves and that spin effects are negligible. This is in sharp contrast to our earlier results obtained by using a magnetic bottle electron spectrometer, in which the ionization process occurred in a 0.5–1.0 T magnetic field [J. L. Dehmer et al., J. Chem. Phys. 90, 6243 (1989)]. It is concluded that the magnetic field can significantly modify the rotational distributions observed for vibrational autoionization. The implications of this conclusion are discussed, with particular attention to other experiments performed with the magnetic bottle spectrometer.

Three-photon electron spectroscopy of nitric oxide through intermediate states in the 66000 cm −1 region

Electron spectra of (2 + 1)-photon ionisation of NO are studied as a function of wavelength. Use is made of the new “magnetic bottle spectrometer”