Search results for "Citation"
showing 10 items of 1710 documents
High resolution spectroscopy and channel-coupling treatment of the A 1Σ+–b 3Π complex of NaRb
2002
The paper presents the study of the fully mixed A 1Σ+–b 3Π complex of the NaRb molecule based on high-resolution sub-Doppler spectroscopy and intensity measurements, ab initio relativistic calculations of energies, transition moments and spin–orbit interactions, as well as an inverted channel-coupling approach (ICCA) deperturbation analysis. A two-laser V-type pump–probe excitation scheme was employed to obtain A←X transition frequencies to 16 A-state vibrational levels from v=6 to v=21 with J from 8 to 23. Additionally, relative intensities in laser-induced A→X fluorescence spectra have been recorded, including progressions with all observable transitions to the ground state vibronic level…
Study of Mechanisms of Light-Induced Dissociation of Ru(dcbpy)(CO)2I2 in Solution down to 20 fs Time Resolution
2006
Mechanisms of the light-induced ligand exchange reaction of (trans-I) Ru(dcbpy)(CO)2I2 (dcbpy = 4,4'-dicarboxylic acid-2,2'-bipyridine) in ethanol have been studied by transient absorption spectroscopy. Ultraviolet 20 fs excitation pulses centered at 325 nm were used to populate a vibrationally hot excited pi bipyridyl state of the reactant that quickly relaxes to a dissociative Ru-I state resulting in the release of one of the carbonyl groups. Quantum yield measurements have indicated that about 40% of the initially exited reactant molecules form the final photoproduct. A 62 fs rise component in the transient absorption (TA) signal was observed at all probe wavelengths in the visible regio…
The first excited singlet state of s‐tetrazine: A theoretical analysis of some outstanding questions
1996
The equation‐of‐motion coupled cluster method for excited electronic states (EOMEE‐CC) is applied to study the structure and selected properties of the first excited singlet state of s‐tetrazine. Adiabatic S1←S0 excitation energies obtained with large basis sets containing up to 270 functions are uniformly somewhat above the experimental 0–0 value of 2.238 eV, but nevertheless are the most accurate calculations reported to date for this quantity. The equilibrium geometry of S1 predicted in this study is in excellent agreement with another high‐level calculation, and moreover is quantitatively consistent with both the intensity of vibrational progressions observed in absorption and measured …
The Ramsey method in high-precision mass spectrometry with Penning traps: Experimental results
2007
The highest precision in direct mass measurements is obtained with Penning trap mass spectrometry. Most experiments use the interconversion of the magnetron and cyclotron motional modes of the stored ion due to excitation by external radiofrequency-quadrupole fields. In this work a new excitation scheme, Ramsey's method of time-separated oscillatory fields, has been successfully tested. It has been shown to reduce significantly the uncertainty in the determination of the cyclotron frequency and thus of the ion mass of interest. The theoretical description of the ion motion excited with Ramsey's method in a Penning trap and subsequently the calculation of the resonance line shapes for differ…
Theoretical study of electronically excited cis- and trans-glyoxal
1997
Abstract The equation-of-motion coupled cluster method for excitation energies in the singles and doubles approximation (EOMEE-CCSD) is applied to an investigation of the structure and harmonic frequencies of planar conformers of glyoxal in their first excited singlet states. For the trans-isomer, agreement between calculated harmonic frequencies and observed fundamentals is generally satisfactory, although the theoretical values are slightly more than 10% too high for the carbonyl stretching modes. Parallel calculations of the corresponding ground state properties allow for an empirical prediction of the excited state frequencies in which calculated differences in normal-mode frequencies a…
Theoretical study of the derivative hydrocarbons of biphenylene. I. Electronic spectrum of the biphenylene
1969
The electronic spectrum of biphenylene has been studied theoretically. The investigation is based on the semi-empirical LCAO SCF MO method with various degrees of approximations. The results have been analysed with regard to the following two factors: (a) The difference in effective electronegativity between the carbon atoms in the four-membered ring and the other carbon atoms in the molecule. (b) The inclusion of doubly excited configurations in the description of the π-electronic molecular states. The theory satisfactorily interprets the excitation energies and the nature of the electronic transitions. The predictions are particularly affected by the inclusion of the doubly excited config…
Excitation modes for fourier transform-ion cyclotron resonance mass spectrometry.
1992
AbstractVarious geometric configurations for the excitation of coherent ion motion in Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR/MS) are analyzed (in some cases for the first time) with unified notation. The instantaneous power absorption, F·v, in which v is ion velocity and F the force produced by the applied excitation electric field (harmonic, single frequency, on-resonance, in-phase), is time averaged and then set equal to the time rate of change of ion total (cyclotron + magnetron + trapping) energy, to yield a differential equation that is readily solved for the (time-dependent) amplitude of each of the various ion motions. The standard FT-ICR excitation (name…
Recombination processes in rare-earth doped MAl2O4(M = Ca, Sr) persistent phosphors investigated by optically-detected magnetic resonance
2007
Single crystalline MAl 2 O 4 (M = Ca and Sr) persistent phosphors, which are nominally pure or additionally doped with Eu and Nd or Dy, respectively, were investigated for their recombination luminescence (RL) and microwave-induced changes in the RL at low temperatures. The analysis of the optically-detected electron paramagnetic resonance (EPR) spectra, recorded after ultraviolet excitation at 4.2 K, shows that intrinsic donor and acceptor centres are involved in the recombination process. Spectral dependent RL-EPR measurements on undoped CaAl 2 O 4 (CAO) and SrAl 2 O 4 (SAO) show that we deal with only one donor but at least two different acceptors. The g value of the donor is 1.99 in CAO…
Oxygen influence on luminescence properties of rare-earth doped NaLaF 4
2016
Abstract Luminescence properties of erbium and europium doped NaLaF4 with different oxygen content have been studied. Vacuum ultraviolet (VUV) excitation luminescence spectroscopy technique has been applied by using synchrotron radiation excitation. It was found that oxygen impurity leads to significant degradation of Er3+ or Eu3+ emission under VUV excitation. The intensive O2−–Er3+ charge transfer excitation band has been detected from oxygen abundant NaLaF4 in the 150–165 nm spectral range. This band reveals a competing absorption mechanism in oxygen containing NaLaF4. It is clearly demonstrated that one reason for the Er3+ emission degradation in oxygen abundant NaLaF4 is strong suppres…
Intrinsic luminescence and energy transfer processes in pure and doped YVO 4 crystals
2007
Luminescence properties of nominally pure and neodymium doped YVO4 single crystals have been studied by means of time-resolved luminescence spectroscopy technique. It was detected that, besides the main well-known blue excitonic emission band near 2.8 eV, an additional UV emission band at ∼3.1 eV appears in the spectra of intrinsic luminescence at low temperatures (∼80 K) for all crystals studied. Decay time of the UV band is much faster in comparison with the blue one and the UV band is quenched at temperatures above 150 K. Origin of the UV emission band is discussed. A significant rise front was observed in the relaxation kinetics of Nd3+ emission under band-to-band excitation. The time c…