Ion Beam Spectroscopy Research Articles

Hyperfine structure of 147,149Sm II by collinear laser-ion-beam spectroscopy.

Collinear laser--ion-beam spectroscopy has been used to measure the hyperfine structure (hfs) of nine metastable even-parity levels (E<15000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) and nine odd-parity levels (EV32000 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) in $^{147}$,149Sm ii. The mass resolution of 1 part in 350 eliminates spectral congestion due to overlapping lines from neighboring isotopes. The kinematic compression of the Doppler width is essential to obtain the necessary spectral resolution (approximately 20 MHz) to completely resolve hfs. An optical pumping scheme is used to differentiate the upper and lower levels of the observed transitions. The resulting magnetic dipole hfs constants, A, for the even-parity states arising from the 4${f}^{6}$${(\mathrm{}}^{7}$F)5d configuration that are nominally more than pure 90% LS coupled have been analyzed in terms of Sandars-Beck effective-operator theory. The analysis shows that these levels actually contain substantial admixture of open-shell s electrons.

Experimental evidence for the imino methyl radical (HCNH˙) by neutralized ion beam spectroscopy

Experimental evidence for the imino methyl radical (HCNH^˙) by neutralized ion beam spectroscopy

A simple and effective stabilization system for collinear laser ion-beam spectroscopy at mass separators

In principle, Collinear Laser Ion-Beam Spectroscopy (CLIBS) needs very efficient stabilization of the laser frequency ν and the ion energy U to obtain high resolution. The requirements on the stabilization of ν and particularly on U are reduced by a differential measuring technique, using a second beam of stable isotopes as a reference. The ions are kept in resonance with ν by monitoring the fluorescence light. The stabilization may act on the ion energy by a post-acceleration system or on ν. The time constant (1 to 0.05 s) depends on the intensity of the reference beam. Instabilities of ν and U with longer time constants do not affect the measurements. As a main advantage this technique is independent of the separator regime and avoids a highly sophisticated stabilization of U. Therefore, we could use our system unaltered at two different mass separators.

Experiences with collinear laser spectroscopy of ion beams from electromagnetic isotope separators

Collinear Laser Ion-Beam Spectroscopy (CLIBS) needs some special precautions with regard to the regime and construction of the electromagnetic isotope separator in order to achieve the high precision and sensitivity possible with this method. Collinearity of the laser and ion beam can be obtained by a well-designed ion optical system and is influenced by the angular dispersion of ions. The knowledge of the kinetic energy of the ions is very important; it depends on the acceleration voltage and the voltage drops in the ion source, the flight tank, and the interaction chamber. The sensitivity depends for instance on the population of the investigated atomic states and is influenced by the ion-source characteristics, by de-excitation during flight and by laser pumping. An increase of sensitivity by further development of this technique is anticipated.

The 2p4 3s, 3p and 3d Configurations of Thirteen Times Ionized Titanium, Ti XIV

The spectrum of Ti XIV has been observed in the wavelength region 80-550 Å using the fast ion beam spectroscopy method. 47 lines have been identified as transitions between the 2p4 3s, 3p, and 3d configurations in the 360-540 Å interval. The level identifications are supported by comparisons between observations and Hartree-Fock calculations along the F I isoelectronic sequence.

Hydrocarbon polymerization on drift chamber wires

A drift chamber which serves as a trigger for the time projection chamber (TPC) at the PEP storage ring at Stanford Linear Accelerator Center became inoperative during beam running due to recurring discharges. Visual examination of chamber wires revealed “whisker” growths and numerous black deposits. More detailed examination by mass spectroscopy and ion beam spectroscopy has shown that polymerized hydrocarbons similar to polyethylene are generally present on all wires. A mechanism relating polymerization and whisker formation is suggested.

Energy partitioning in He2+/K collisions

Final state distributions and state-specific reaction cross sections for 1.5–6 keV He2+/K collisions have been determined from data acquired using both neutralized ion beam spectroscopy and direct observation of luminescence from decay of excited collision products. While several minor reaction channels can be identified, it is found that near-resonant processes yielding He2(a 3Σu+) and He2(A 1Σu+) are predominant. These major channels, both of which have cross sections in excess of 100 Å2, lead to substantial production of energetic metastable molecules and VUV continuum radiation extending from about 750 to 850 Å.

Experimental evidence for metastable states of D3O and its monohydrate by neutralized ion beam spectroscopy

The oxonium radical (H3O) has been generated in its ground state by neutralizing a fast beam of ions in the near resonant electron transfer reaction H3O++K(g)→H3O*+K+. Analysis of neutral beam scattering profiles and collisionally reionized mass spectra indicate that the fully deuterated species (D3O) can be formed in a distribution of dissociative and metastable states (τ>0.6 μs). Thermalization of the precursor D3O+, prior to electron transfer, is required for production of metastable D3O. Neither H3O nor D2HO is observed in metastable states. These isotope effects support earlier theoretical predictions of a shallow local minimum on the oxonium potential surface. The ionization potential of D3O is calculated to be 4.3±0.1 eV. Some spectroscopic implications for this radical are discussed. The oxonium monohydrates (H3O⋅H2O) are also observed to exist in metastable states for several H/D isotopic variants. The ionization potential of D3O⋅D2O is estimated to be ≥3.4 eV.

An experimental study of hypervalent molecular clusters by neutralized ion beam spectroscopy: ammonium-ammonia (NH4(NH3)n) and deuterated ammonium-ammonia (ND4(ND3)n)

An experimental study of hypervalent molecular clusters by neutralized ion beam spectroscopy: ammonium-ammonia (NH4(NH3)n) and deuterated ammonium-ammonia (ND4(ND3)n)

Investigations of europium isotopes with neutron numbers between 84 and 93 by collinear laser ion-beam spectroscopy

Hyperfine structures and isotope shifts of the transition Eu II 4f7(8S72/O)6p3/2 (7/2,3/2)4 — 4f7 (8S72/O)5d9D4O,λ=6O4.95 nm, of the radioactive isotopes147, 149, 155, 156Eu have been studied by collinear laser-ion beam spectroscopy (CLIBS). The nuclear moments and the differences of the mean square nuclear charge radii as well as the deformation parameters have been deduced. The experimental data for the odd-A nuclei are in a good agreement with simple Nilsson model calculations.

Nuclear moments and isotope shifts of europium isotopes by hyperfine structure investigations with collinear laser ? Ion beam spectroscopy

Hyperfine structures and isotope shifts of the transition 4f7(8S72/0)6p3/2 (7/2,3/2)4−4f7(8S72/0) 5d9D40,λ=604.95 nm, of stable151Eu and153Eu and radioactive152Eu and154Eu have been investigated by collinear laser — ion beam Spectroscopy. Nuclear quadrupole moments have been derived.

Neutralized ion-beam spectroscopy

Research on the neutralization of ion beams by electron-capture collisions with atomic particles has largely been within the domain of atomic and high-energy physics with the emphasis on understanding the fundamentals of ion-atom interactions. This account presented a chemist's perception of the possibilities to obtain new information about molecules formed by neutralization of beams of molecular ions. Only reactions in which a molecule is formed in an electron-capture process are discussed. In this article neutralized ion beam spectroscopy was defined as a technique for investigating modes of energy disposal in species formed when a fast beam of ions is neutralized in the electron-transfer reaction AB/sup +/ + M(g) ..-->.. AB* + M*/sup +/ where AB/sup +/ is any diatomic or polyatomic ion and M is a thermalized target atom. The target atom series M = Cs, K, Na, Ca, Mg, and Zn that covers an ionization potential range of 3.9 to 9.4 eV. The most significant technical advance from neutralized ion beam studies is the capability of producing beams of stable or metastable molecules that would be difficult, if not impossible, to obtain by other methods. 5 figures, 2 tables. (DP)

ChemInform Abstract: AN EXPERIMENTAL STUDY OF THE BRIDGED AND CLASSICAL STRUCTURES OF THE ETHYL RADICAL AND CATION BY NEUTRALIZED ION‐BEAM SPECTROSCOPY

Chemischer InformationsdienstVolume 14, Issue 22 Preparative Organic Chemistry ChemInform Abstract: AN EXPERIMENTAL STUDY OF THE BRIDGED AND CLASSICAL STRUCTURES OF THE ETHYL RADICAL AND CATION BY NEUTRALIZED ION-BEAM SPECTROSCOPY G. I. GELLENE, Search for more papers by this authorN. S. KLEINROCK, Search for more papers by this authorR. F. PORTER, Search for more papers by this author G. I. GELLENE, Search for more papers by this authorN. S. KLEINROCK, Search for more papers by this authorR. F. PORTER, Search for more papers by this author First published: May 31, 1983 https://doi.org/10.1002/chin.198322137AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue22May 31, 1983 RelatedInformation

An experimental study of the bridged and classical structures of the ethyl radical and cation by neutralized ion-beam spectroscopy

The states of ethyl radicals formed in electron capture reactions of a fast beam of C2H5+ with a series of metal target atoms (K, Na, Ca, Mg, and Zn) have been investigated by neutral beam scattering techniques. Reactions of C2H5+ with Mg or Zn atoms lead to formation of ground state radicals and an excited state about 0.5 eV above the dissociation limit of C2H4+H. Analysis of branching ratios for these processes over a range of Mg atom densities shows that the ion beam is a mixture of two isomers in the ratio of about 7.3/1.0 for beams generated either by electron impact or chemical ionization methods. From neutral-precursor ion relationships we propose that the major and minor components of the ion beam are the bridged and classical C2H5+ structures, respectively. Analysis of neutral beam profiles in experiments with Na or K targets indicate the formation of a dissociative state of the classical radical lying about 4.2 eV above the ground state. An upper limit of 2.2 eV to the barrier to 1, 2 hydrogen migration in the classical radical is provided by the energy of the lowest state of the bridged radical observed.

Two-electron capture into autoionising states of N5+(3l3l') and O5+(1s3l3l') in collisions of N7+and O5+with He

Transfer ionisation processes are studied for the N7++He and O7++He systems by means of ion beam spectroscopy at 7 keV. The autoionising states (3l3l') of N5+ and (1s3l3l') of O5+ are identified.

Stability of the ammonium and methylammonium radicals from neutralized ion-beam spectroscopy

The stability of the ammonium radical (NH4) was determined from measurements of the kinetic energy released in its fragmentation products following formation in a fast electron capture process: NH4++Na → NH4*+Na+. Scattering profiles for heavy (NH3) and light (H) dissociation products were obtained from beam measurements with 5–16 keV NH4+ ions. The existence of a predissociative barrier in the radical is inferred from edge structure and scattering continua in H atom profiles. The radical is bound with respect to a potential minimum but all of the isotopic species NH4, NH3D, NH2D2, and NHD3 undergo rapid loss of H atoms and have ground states lying above their dissociation limits. The radical ND4 has unusual stability with its ground state lying close to or below its dissociation limit. Dissociative lifetimes for stable and unstable states of ND4 differ by at least two orders of magnitude. The possible significance of these observations on the interpretation of optical transitions involving the ground states of NH4 and ND4 are discussed. From these measurements the ionization potential of 4.73±0.06 eV for NH4 is calculated. The stabilities of CH3NH3 and CH3ND3 radicals and their dissociative pathways have also been investigated.

Ion Beam Spectroscopy of Solids and Surfaces

Ion beams are important new probes for characterizing the chemistry and structure of a wide variety of materials. When beams of particles with energies of approximately 1000 electron volts are used, as in secondary ion mass spectrometry, it is possible to detect ions ejected from the top layer of the material with sensitivities we below the picogram level. A number of theoretical developments now permit analysis of the geometry of adsorbed atoms and molecules on surfaces from the angular distributions of the ejected particles. Much surface chemical information can also be deduced from ejected molecular cluster ions. In addition, the observation of clusters with weights up to nearly 20,000 atomic mass units promises to expand applications of mass spectrometry to the analysis of biomolecules and the sequencing of proteins.

Depth profiling by ion-beam spectrometry

A procedure is developed for determining the stoichiometry of a sample as function of depth from ion-beam analysis energy spectra. The approach is in principle equally applicable to back scattering experiments, experiments involving nuclear reactions with known cross sections and experiments combining these techniques. The procedure is especially suitable for routine computer evaluation of energy spectra. It is more straightforward and/or involves less rigid assumptions and approximations than alternative approaches. If all elemental signals are measured, an accurate beam dose is not needed. The limitations are basically those inherent to ion beam analysis in general.

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Surface Science Studied by Ion Beam Spectroscopy

Instruments for surface analyses have greatly improved in the past ten or twenty years. the ion beam technique which has been utilized in the field of nuclear physics. has grown up to a powerful tool for the surface analysis, In this Current Topics, applications to surface science are reviwed. of the backscattering and channeling methods, and of ion-induced X-ray and Auger electron spectroscopies