Search results for "ionization"
showing 10 items of 1255 documents
Principle and analytical applications of resonance lonization mass spectrometry
1989
Resonance ionization mass spectrometry (RIMS) is a very sensitive analytical technique for the detection of trace elements. This method is based on the excitation and ionization of atoms with resonant laser light followed by mass analysis. It allows element and, in some cases, isotope selective ionization and is applicable to most of the elements of the periodic table. A high selectivity can be achieved by applying three step photoionization of the elements under investigation and an additional mass separation for an unambiguous isotope assignment. An effective facility for resonance ionization mass spectrometry consists of three dye lasers which are pumped by two copper vapor lasers and of…
Comparative optical reflection and mass spectrometry analysis of thermodesorption of Langmuir-Blodgett films
1992
Abstract Thermodesorption of cadmium arachidate multilayers is studied by optical surface analysis and by mass spectrometry measurements. The optical reflection technique has been improved to discriminate signal contributions from desorption and light scattering. The scattering arises from film heterogeneities that are also observed by Nomarsky microscopy. The assessment of these heterogeneities is important to understand mass spectrometry data. Both the optical technique and mass spectrometry are sensitive to observing the multilayer phase transition at 110 °C and the desorption near 200 °C (at the heating rate applied). The mass spectrometry analysis yields detailed information on the des…
Quantum correlations in generalized spin star system
2006
The problem of detecting quantum signatures in the correlations formed in dynamical evolution of quantum bipartite systems receives a lot of attention in current literature. Generally speaking, the occurrence of correlations between two observables of a system does not necessarily reflect nonclassical behaviour. In this paper, the exact dynamics of a pair of uncoupled spins 1/2 interacting with a common spin 1/2 bath is investigated. Starting from a separable initial condition, the ability of the system to develop purely quantum correlations is brought to light. Physical interpretation of the concurrence function as well as a suggestion on how to measure it are given.
Spectrum emitted by a trapped electron
2007
We study the behaviour of a homonuclear molecule driven by an intense laser field. Newton's laws are used to describe the dynamics of nuclei while the quantal approach is reserved to the study of the electron. It is observed that the nuclei can oscillate or dissociate according to the degree of ionization of the molecule. In case of low ionization rate it is shown that great amount of information can be obtained by using the simplified approaches of fixed nuclei and of two-state approximation. Under suitable conditions the electron wave function spends a long time localized around one nucleus. The harmonic generation of the molecule is studied and seen to contain even harmonics.
Recognition of Li+ by a Salophen−UO2 Homodimeric Complex
2009
Self-assembly via mutual U-coordination of the salophen-UO(2) complex 1 creates a dimeric species which is shown to be useful for metal binding. Indeed, the 1 dimer has affinity for alkali metal cations and, interestingly, a marked selectivity for Li(+), determined by electrospray ionization mass spectrometry and (1)H NMR techniques. X-ray diffraction helped in the elucidation of the dimeric complex structure, which presents a crown-ether-type coordination site, in analogy to the more familiar 12-crown-4, responsible for the metal interaction. Comparison with isomer 2, and the salen derivative 3, increases the understanding of the behavior of such systems in solution and in the solid state.
Triple bridged μ-phenoxo-bis(μ-carboxylate) and double bridged μ-phenoxo-μ1,1-azide/μ-methoxide dicopper(II) complexes: Syntheses, structures, magnet…
2013
Abstract The work in this paper presents syntheses, characterization, crystal structures, catecholase activity, electrospray ionization mass spectroscopy (ESI-MS positive), and magnetic properties of seven triple bridged μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes [CuII2L(μ-HCOO)2](ClO4)·CH3OH (1), [CuII2L(μ-CH3COO)2](ClO4) (2), [CuII2L(μ-CCl3COO)2(H2O)](ClO4) (3), [CuII2L(μ-CH3CH2COO)2](ClO4) (4), [CuII2L(μ-CH3CH2CH2COO)2](ClO4) (5), [CuII2L(μ-PhCOO)2](ClO4)·CH3CN (6) and [CuII2L(μ-o-ClPhCOO)2](ClO4) (7), one double bridged μ-phenoxo-μ1,1-azide system [CuII2L(μ1,1-N3)(N3)2] (8) and one double bridged μ-phenoxo-μ-methoxide system [CuII2L(μ-OCH3)(NCO)2] (9), derived from a new dinucl…
Mass spectra of methoxychlorobenzenes (chloroanisoles)
1988
Electron impact mass of all 19 ring-substituted chloroanisoles have been investigated. The fragmentation pathways were elucidated with the aid of the 1st field-free region metastable ions. The greatest disparity between the spectra of the positional isomers is shown with the [M−CH 3 ] + and [M−CH 2 O] +• ions, i.e., the ortho and para isomers preferentially lose • CH 3 , whereas the meta isomers generally show both loss of • CH 3 and elimination of formaldehyde, the latter process being more dominant with the meta-monochloro and di- and trichloro isomers having two meta-chlorine atoms. Characteristic for all isomers is also the abundant M +• and [M−CH 3 −CO] + ions, the other fragmentation …
Determination of the electron-detachment energies of 2'-deoxyguanosine 5'-monophosphate anion: influence of the conformation.
2009
The vertical electron-detachment energies (VDEs) of the singly charged 2'-deoxyguanosine 5'-monophosphate anion (dGMP - ) are determined by using the multiconfigurational second-order perturbation CASPT2 method at the MP2 ground-state equilibrium geometry of relevant conformers. The origin of the unique low-energy band in the gas phase photoelectron spectrum of dGMP - , with maximum at around 5.05 eV, is unambiguously assigned to electron detachment from the highest occupied molecular orbital of π-character belonging to guanine fragment of a syn conformation. The presence of a short H-bond linking the 2-amino and phosphate groups, the guanine moiety acting as proton donor, is precisely resp…
Diphenyltin(IV) complexes of the 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-olates: Synthesis and multinuclear NMR, 119Sn Mössbauer, electrospray ionizati…
2006
Abstract A series of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}diphenyltin(IV) complexes have been synthesized and characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mossbauer spectroscopic techniques in combination with elemental analysis. The structures of a ligand L6H (i.e., 5-[(E)-2-(4-ethoxyphenyl)-1-diazenyl]quinolin-8-ol) and three diphenyltin(IV) complexes, viz., Ph2Sn(L1)2 · (CH3)2CO (1), Ph2Sn(L4)2 (4) and Ph2Sn(L5)2 (5) (L = 5-[(E)-2-(aryl)-1-diazenyl]quinolin-8-ol: aryl = phenyl – (L1H); 4′-methylphenyl – (L4H) and 4′-bromophenyl – (L5H)) were determined by single crystal X-ray diffraction. In general, the complexes were found to adopt a distorted cis-octahedral a…
Mass spectra of halogenated esters. Part IX—methyl esters of 2-butenoic acids containing chlorine and/or bromine atom(s)
1990
The electron impact mass spectra of methyl esters of chloro-, bromo-, dichloro-, bromochloro- and dibromo-2-butenoic acids (13 esters at all) have been investigated. Generally, the peaks due to the following fragments are abundant: M+·, [M OCH3]+, [M CH3OH]+·, [M X]+, [M OCH3 CO]+ or [M COOCH3]+, [M X CH3OH]+ or [M OCH3 HX]+, [M OCH3 CO HX]+, [M OCH3 X X]+ and [M OCH3 CO X X]+. Characteristic for the 2- and 4-halo isomers are the primary losses of a methyl radical and methanol, and for the 3-halo isomers the loss of X· from M+·. Disparities between the spectra of the E and Z isomers are shown, the effect of position of halogen substitution being much more pronounced, as reported previously …