Magnetic Bottle Electron Research Articles

Site-specific Auger electron spectra of ethyl trifluoroacelate molecules studied by magnetic bottle electron spectrometer

We performed multielectron coincidence measurements for inner-shell photoionizations of ethyl trifluoroacelate molecules (C4H5F3O2) using a magnetic bottle electron spectrometer. From a two dimensional coincidence map between a photoelectron and Auger electron for C 1s ionizations, we extracted site-specific Auger electron spectra for each carbon site and corresponding binding energy of doubly charged states.

A magnetic-bottle multi-electron-ion coincidence spectrometer

A novel multi-electron-ion coincidence spectrometer developed on the basis of a 1.5 m-long magnetic-bottle electron spectrometer is presented. Electrons are guided by an inhomogeneous magnetic field to a detector at the end of the flight tube, while a set of optics is used to extract counterpart ions to the same detector, by a pulsed inhomogeneous electric field. This setup allows ion detection with high mass resolution, without impairing the high collection efficiency for electrons. The performance of the coincidence spectrometer was tested with double ionization of carbon disulfide, CS(2) → CS(2)(2+) + e(-) + e(-), in ultrashort intense laser fields (2.8 × 10(13) W/cm(2), 280 fs, 1030 nm) to clarify the electron correlation below the rescattering threshold.

Energy Correlation among Three Photoelectrons Emitted in Core-Valence-Valence Triple Photoionization of Ne

The direct observation of triple photoionization involving one inner shell and two valence electrons is reported. The energy distribution of the three photoelectrons emitted from Ne is obtained using a very efficient multielectron coincidence method using the magnetic bottle electron spectroscopic technique. A predominance of the direct path to triple photoionization for the formation of Ne3+ in the 1s 2s2 2p4 configuration is observed. It is demonstrated that the energy distribution evolves with photon energy and indicates a significant difference with triple photoionization involving only valence electrons.

Multielectron spectroscopy: Auger decays of the krypton3dhole

The emission of one or two Auger electrons, following Kr $3d$ inner-shell ionization by synchrotron light, has been investigated both experimentally and theoretically. All electrons emitted in the process are detected in coincidence and analyzed in energy thanks to a magnetic-bottle electron time-of-flight spectrometer. In addition, noncoincident high-resolution electron spectra have been measured to characterize the cascade double-Auger paths more fully. Combination of the two experimental approaches and of our calculations allows a full determination of the decay pathways and branching ratios in the case of Kr $3d$ single- and double-Auger decays. The ${\mathrm{Kr}}^{3+}$ threshold is found at $74.197\ifmmode\pm\else\textpm\fi{}0.020$ eV.

Photoelectron spectroscopy ofO−at 266 nm: Ratio of ground- and excited-state atomic oxygen production and channel-resolved photoelectron anisotropy parameters

The photodetachment dynamics of the atomic oxygen anion ${\mathrm{O}}^{\ensuremath{-}}$ has been investigated at 266 nm (4.67 eV) by photoelectron detection in a crossed-beam experiment using a magnetic-bottle electron spectrometer. Taking explicit advantage of the Doppler shift imposed by the moving ion beam on the photoelectron energies, we report both the final-state branching ratio and photoelectron angular distributions. After photoabsorption at 266 nm, the formed electron-oxygen scattering state disintegrates, forming either the excited ${}^{1}D$ or the ground ${}^{3}P$ state of oxygen with a partition of ${}^{1}D$:${}^{3}P=0.32$ $\ifmmode\pm\else\textpm\fi{}$ 0.06. The detachment leading to the production of O(${}^{3}P$) shows an angular distribution of photoelectrons characterized by ${\ensuremath{\beta}}_{P}=0.00$ $\ifmmode\pm\else\textpm\fi{}$ 0.10 mimicking a pure s-wave detachment, while the detachment into excited O(${}^{1}D$) occurs with ${\ensuremath{\beta}}_{D}=\ensuremath{-}0.90\ifmmode\pm\else\textpm\fi{}0.10$, giving direct evidence of interference between the outgoing $s$ and $d$ waves.

Multiple photoionization of atoms and small molecules by synchrotron radiation

Absorption of one VUV photon by an atom or a molecule can induce the ejection of several electrons through different processes. Such multiple ionization processes, studied by coincidence electron spectroscopy, provide a wealth of information on electron correlations. A magnetic bottle electron time of flight spectrometer implemented on synchrotron radiation centers has allowed the efficient detection in coincidence of two, three and up to five electrons with good energy resolution. The branching ratios of the different processes are easily extracted from the experimental spectra due to the constant transmission of the spectrometer. Multiple Auger decay was observed in rare gases atoms after inner-shell ionization, while core-valence and core-core initial double ionization followed by Auger decay are other pathways to multiple ionization. For molecules, Coulomb explosion with energy released in ionic fragments may occur after multiple ionization, nevertheless, coincidence electron spectroscopy can also provide a clear interpretation for peculiar decay channels in molecules.

Multi-coincidence in cascade Auger decay processes

Two-electron emission following inner shell ionization of rare-gas atoms by synchrotron radiation has been investigated experimentally with a magnetic bottle electron time of flight spectrometer. The detection in coincidence of a photoelectron with all Auger electrons allows a complete understanding of inner shell hole decay. This method has been applied to the study of single and double Auger decays following Xe 4d, Ar 2p and Kr 3d inner shell ionization. The double Auger decay scheme reveals direct double Auger process but is dominated by cascade processes involving inner-valence electrons in a first step followed by autoionization. Post collision interaction (PCI) associated to distorted Auger spectra and double photoionization paths in the vicinity of Xe 4d threshold, is also discussed.

Studies of double photoionisation using a fast pulsed VUV source

A lamp giving 5 ns pulses of 10–50 eV photons at 10 kHz repetition rate has been developed and used with a magnetic bottle electron time-of-flight (TOF) spectrometer to study double photoionisation of atoms and molecules. In addition to the spectra of the dications and complete electron pair energy distributions, quantum yields of double ionisation, as defined in this paper, can be determined. Electron pair energy distributions in double photoionisation of Hg, N 2 and CS 2 are presented as representative of results on many other atoms and molecules. Double photoionisation is found to be mainly indirect, dominated by autoionisation of intermediate monocations, for complex atoms, but mainly direct for small molecules in the valence energy range. The difference arises because superexcited states of molecular monocations decay by dissociation to singly charged products.

Penning ionization electron spectroscopy of van der Waals clusters

Abstract A magnetic bottle electron spectrometer with retarding electrodes has been applied to observation of Penning ionization electron spectra (PIES) of van der Waals clusters. Considerably increased efficiency of the spectrometer by 1000 times over the conventional PIES apparatus enabled us to measure electron spectra of van der Waals clusters of rare gas atoms in collisions with metastable atoms, He*(2 3 S) and Ne*(3 3 P). Unusually fast electrons with extra kinetic energies of 1–2 eV as compared to those expected for vertical ionization have been detected for Ar and Kr van der Waals clusters in collisions with He*(2 3 S). These fast electrons are ascribed to autoionization into stable ionic structures via superexcited states embedded in the ionization continua, and the unusual electrons can be considered to be related to an adiabatically ionized state to which a direct ionization process is almost forbidden because of a very small Franck–Condon factor.

Observation of collisional ionization electron spectra of van der Waals clusters with metastable He*(2 3S) atoms: An evidence for autoionization from superexcited Ar clusters

Penning ionization electron spectra (PIES) of van der Waals clusters have been observed for the first time by means of a newly developed magnetic bottle electron spectrometer, which is 1000 times more efficient than a conventional PIES apparatus. In the PIES of Ar clusters with He*(2 3S), two bands of Ar 3p hole characters with different ionization energies (IE), band A (IE=ca.15 eV) and band B (IE=ca.13.5 eV), were observed. Band A was assigned to vertical transitions in Franck–Condon regions corresponding to the band in the ultraviolet photoelectron spectra (UPS) of clusters reported by Carnovale et al. [J. Chem. Phys. 90, 1452 (1989)]. Band B, which is an extra band missing in the UPS of clusters, can be ascribed to the autoionization into a stable structure of Arn+ via superexcited states of Arn. Band B can be considered as an adiabatic ionization which is forbidden as a direct ionization. The energy difference of ca. 1.5 eV between the vertical IE for band A and the adiabatic IE for band B was found to agree well with the reported binding energy of the trimer ion core.

Double-resonance spectroscopy of autoionizing states of ammonia

New double-resonance ionization data are presented on the autoionizing Rydberg states of NH3 excited via selected rotational levels of the C̃′ 1A1(0100) and (0200) states. Extrapolation of the Rydberg series provides a determination of the adiabatic ionization energy of NH3 that is in excellent agreement with that obtained by using zero kinetic energy photoelectron spectroscopy (ZEKE-PES). A comparison is presented between the field-free spectrum obtained by using a time-of-flight mass spectrometer and the 1-Tesla-spectrum obtained by using a magnetic-bottle electron spectrometer. Finally, the rotational and vibrational autoionization mechanisms are discussed.

Vibrational autoionization and predissociation in high Rydberg states of nitric oxide

New results on the competition between autoionization and predissociation in the high Rydberg states of nitric oxide are presented. These results provide insight into the earlier work of Park et al. [Phys. Rev. Lett. 76, 1591 (1996)] that shows evidence for substantial mixing between Rydberg series and ionization continua with even and odd orbital angular momenta (l). New data based on fluorescence-dip spectroscopy, detection of neutral predissociation products, and photoelectron spectroscopy suggest that the A′ 2Σ+ and I 2Σ+ dissociative valence states play an important role in this l mixing. Zeeman splittings observed in a magnetic bottle electron spectrometer also result in an improvement in the assignment of these high Rydberg states.

PHOTOELECTRON SPECTROSCOPY OF BINARY-METAL CLUSTER ANIONS CONTAINING SULFUR ATOM

Photoelectron spectra of [Formula: see text] (M= Al , Cu, Ag, and Au) cluster anions were measured at the photon energies of 3.49 and 4.66 eV using a magnetic-bottle electron spectrometer having ~60-meV resolution. The electron affinities of AlS−, CuS−, AgS−, and AuS− are 2.60(3), 2.10(3), 2.09(3), and 2.44(3) eV, respectively. The large EA of AlS− is attributed to large stability by six bonding electrons, and a new electronic state of A ′ 2Π can be found 0.4 eV above the AlS ground state, which is in agreement with a theoretical calculation. In the photoelectron spectrum of AuS−, two peaks due to a splitting by the L–S coupling could be observed, and the amount of the splitting is 0.18(2) eV. The results of aluminum clusters containing sulfur atom will also be presented.

PHOTOELECTRON SPECTROSCOPY OF SILICON–CARBON CLUSTER ANIONS

Photoelectron spectra of [Formula: see text] cluster anions (3≤n, m≤6) were measured at the photon energy of 3.49 eV, by using a magnetic-bottle electron spectrometer having ~60-meV resolution. The [Formula: see text] clusters were produced by laser vaporization of a carbon–silicon mixture rod in a He carrier gas. The spectra of the [Formula: see text] clusters are similar to those of pure [Formula: see text] clusters in the peak positions and their envelopes, which is attributed to the similarity in electronic structure of Si and C atoms, leading to a similar geometry. In contrast, the similarity in the photoelectron spectra is not observed between [Formula: see text] and [Formula: see text] clusters, which is attributed to a change in their geometry; from chain to ring.

Photoelectron spectroscopy of silicon–carbon cluster anions (SinC−m)

Photoelectron spectra of SinC−m cluster anions (1≤n≤7 and 1≤m≤5) were measured at the photon energies of 3.49 eV, by using a magnetic bottle electron spectrometer. The SinC−m clusters were produced either by a laser vaporization of a silicon–carbon mixed rod or by two laser vaporizations of carbon and silicon rods in a He carrier gas. The spectra of the SinC−1 (3≤n≤7) clusters are similar to those of pure Si−n+1 clusters in the peak positions and their envelopes, which is attributed to the isovalent electronic structure of Si and C atoms as well as to the similar geometrical structure. In contrast, the similarity in the photoelectron spectra is not observed between C−m+1 and Si1C−m (2≤m≤5) clusters, which is attributed to a change in their geometry; from chain to ring. These experimental conclusions are discussed with the results of our theoretical calculations.

Photoelectron spectroscopy and mass distributions of aluminum-sulfur cluster anions (AlnSm−)

Photoelectron spectra of AlnSm− cluster anions (0 ≤ n, m ≤ 10) were measured at photon energies of 3.49 and 4.66 eV, by using a magnetic bottle electron spectrometer. The AlnSm−. clusters were produced by laser vaporization of an aluminum-sulfur mixed rod in He carrier gas. The abundant AInSM clusters are three types of AlS−(Al2S3)k, AlS2−(Al2S3)k, and (Al2S3)k− , where an unit of Al2S3 aggregates with ion cores of AlS−, AlS2−, and Al2S3 , respectively. Al3S3 is exceptionally stable with its geometrical structure.

Photoelectron spectroscopy of AlnS1− clusters (n=1−9)

Photoelectron spectra of AlnS−1 (1≤n≤9) cluster anions were measured at the photon energies of 3.49 and 4.66 eV, using a magnetic bottle electron spectrometer having ∼60 meV resolution. AlS− has an electron affinity of as large as 2.6 eV, attributed to large stability by six bonding electrons. A new electronic state, A′ 2Π, was found 0.4 eV above the AlS ground state, which is in agreement with theoretical calculations. AlnS−1 cluster anions are produced efficiently up to n=5, but the production of larger cluster sizes is found difficult. The mass distribution of AlnS−1 cluster anions and electron binding energy can be explained by a geometric structure obtained by theoretical calculation.

Photoelectron Spectroscopy of AlS− Diatomic Anion

Abstract Photoelectron spectra of AlS− radical were measured using a magnetic bottle electron spectrometer. Electron affinity of AlS was determined to be 2.60(3) eV, and a new electronic excited state, A′2Π, was found 0.4 eV above the AlS ground state, which is consistent with theoretical calculations.

Photoelectron spectroscopy of iron carbonyl cluster anions (Fe n(CO) −m, n = 1−4)

Photoelectron spectra of iron-carbonyl cluster anions (Fe n (CO) − m ) were measured in the gas phase at the photon energy of 4.66 eV, using a magnetic bottle electron spectrometer. The iron-carbonyl cluster anions were produced by slow electron attachment of less than 1 eV to a supersonic expansion of Fe(CO) 5 seeded in a He carrier gas. The photoelectron spectra of the Fe n (CO) − 5 n−1 anions show unresolved broad features, and the threshold energy ( E T) and the vertical detachment energy (VDE) were determined: The E T of Fe n (CO) − 5 n−1 gradually increases by 0.1–0.3 eV with the cluster size. The study suggests that the iron carbonyl cluster anions produced are van der Waals clusters, in which Fe(CO) − 4 works as an ion core.

Photoelectron spectroscopy of (C 6F 6) −n and (Au-C 6F 6) − clusters

Photoelectron spectra of hexafluorobenzene (C 6F 6) cluster anions and its Au complex anion were measured in the gas phase at the photon energy of 3.49 eV, using a magnetic bottle electron spectrometer having ≈ 80 meV resolution. The spectra show unresolved broad features: The vertical detachment energies (VDEs) were determined from the maxima of the spectra. The VDE of (C 6F 6) − n gradually increases by 0.1–0.2 eV with the cluster size ( n=1–8) from 1.56(3) to 2.54(6) eV, and the VDE of (Au-C 6F 6) − anion is 1.99(5) eV.