This work proposes a theoretical study of the Li(2p <- 2s) photoabsorption spectra perturbed by ground hydrogen atoms. The temperature effect on the far-wing spectra is examined in the temperature range 4000-20 000 K. For this purpose, the ground and excited LiH potential curves and the transition dipole moments that connect them are constructed from ab initio data. The investigation shows that the profile spectra are dominated at all temperatures by the singlet A <- X transitions and exhibit in the red wing a satellite structure near the wavelength 1000 nm. The spectra revealed also the appearance beyond 14 000 K of a second satellite structure in the blue wing close to the wavelength 510 nm originating from the triplet c <- a transitions.

Quantal calculations are performed to determine the absorption profile of the broadened potassium resonance line 4p <- 4s in its far wings provoked by helium perturbers. First, the X-2 Sigma(+), A(2)Pi, and B-2 Sigma(+) potentials, as well as the transition dipole moments, are carefully computed through ab initio methods, based on state-averaged complete active space self-consistent field multireference configuration interaction (SA-CASSCF-MRCI) calculations involving the Davidson and basis-set superposition error (BSSE) corrections. The data are then used to generate the KHe photoabsorption spectra and to examine their behavior with temperature. The theoretical profile is dominated by the free-free transitions and exhibits, in the vicinity of the wavelength position of 693 nm, a satellite peak in the blue wing attributed to the B <- X transitions. The results are compared with previous theoretical and experimental investigations and, in general, good agreement is found.

Introduction: It is widely accepted that forward and reflected readouts may not be combined into a single series of EPSI k-spaces [1,2]. Consequently, measurements must be repeated with opposite readout polarities to form two separate k-space series homogenously containing either forward or reflected ADCs. With modern hardware compensation of eddy-currents during the ramptimes of trapezoidal gradient pulses, the plateaus of the forward and reflected readouts may be assumed to be sufficiently flat for the combination of ADCs in a single k-space. Since the remaining echo shifting is independent of the chemical composition of the sample, the strong signal of water may be used as a probe without the need for signal accumulation. Template corrections employed for imaging with EPI enable a zeroand firstorder phase correction in the half-Fourier space by comparing successive readouts obtained without phase encoding blips. Chemical shift evolution during the EPSI sequence complicates the comparison of phase from ADCs acquired at different time, and ignoring this contribution may introduce a Nyquist ghost in the FID. Crisscrossing (it. intreciatta, fr. entrechat) the acquisition of two separate template scans with opposite readout polarities permits the comparison of forward and reflected template ADCs that were acquired during two separate TRs but at the same time in the FID. An additional difficulty inherent to MRSI is the low spatial resolution and the use of voxels of interest combined with saturation bands. All together, they may lead to half-Fourier template lines with limited numbers of significant points from which the phase slope could be determined, or to failed unwrapping across saturated regions. In this study, we suggest to determine the echo-shifting correction by comparing forward template ADCs with corrected reflected template ADCs in k-space.

High-resolution magic angle spinning (HRMAS) Nuclear magnetic resonance (NMR) 1H spectroscopy is playing an increasingly important role for diagnosis. This technique enables setting up metabolite profiles of ex vivo pathological and healthy tissue. Automatic quantitation of HRMAS signals provides reliable reference profiles useful to monitor diseases and pharmaceutical follow-up. However for several metabolites, the values of chemical shifts of proton groups may slightly differ according to the microenvironment in the tissue or cells, in particular to its pH. This hampers accurate estimation of the metabolite concentrations mainly when using quantitation algorithms based on a metabolite basis-set: the metabolite fingerprints are not correct anymore. In this work, we propose an accurate method based on quantum mechanical (QM) simulations. The proposed algorithm automatically corrects mismatches between the signal under analysis and the signals of the simulated basic-set by modifying the basis-set signals. In the optimization procedure, the basis-set signals are simulated again by varying the chemical shifts of metabolites in the QM procedure. Cross-correlation was used as cost function to measure how well the signals match each other. The proposed method, QM-QUEST, provides more robust fitting while limiting user involvement and respects the correct fingerprints of metabolites. Its efficiency is demonstrated by accurately quantitating signals from tissue samples of human brains with oligodendroglioma. (C) 2011 Elsevier Masson SAS. All rights reserved.

A. Lazariev, A-R. Allouche, M. Aubert-Frécon, F. Fauvelle, K. Elbayed, M. Piotto, I. J. Namer, D. van Ormondt, and D. Graveron-Demilly Creatis-LRMN, Université Claude Bernard Lyon 1, Villeurbanne, France, LASIM, Université Claude Bernard Lyon 1, Villeurbanne, France, CRSSA/BCM, Grenoble, France, Institut de Chimie, Strasbourg, France, Bruker BioSpin, Wissembourg, France, Department of Biophysics and Nuclear Medicine, University Hospitals of, Strasbourg, France, Delft University of Technology, Delft, Netherlands

H-1 nuclear magnetic resonance spin-Hamiltonian parameters: chemical shifts delta and indirect spin-spin coupling constants J, have been calculated for serine, a brain metabolite. Serine molecules in the gas-phase as well as in solution in water have been investigated using density functional theory. Solvent and conformer effects as well as zero-point vibrational corrections have been taken into account. For the non-vibrating molecule, the best agreement is obtained when solvent and conformer effects are included. Zero-point vibrational corrections improve the agreement with experimental values, leading to a root mean square deviation of 0.05 ppm for chemical shifts and 0.7 Hz for spin-spin coupling constants.

High-resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) is playing an increasingly important role for diagnosis. This technique enables setting up metabolite profiles of ex vivo pathological and healthy tissue. The need to monitor diseases and pharmaceutical follow-up requires an automatic quantitation of HRMAS 1H signals. However, for several metabolites, the values of chemical shifts of proton groups may slightly differ according to the micro-environment in the tissue or cells, in particular to its pH. This hampers the accurate estimation of the metabolite concentrations mainly when using quantitation algorithms based on a metabolite basis set: the metabolite fingerprints are not correct anymore. In this work, we propose an accurate method coupling quantum mechanical simulations and quantitation algorithms to handle basis-set changes. The proposed algorithm automatically corrects mismatches between the signals of the simulated basis set and the signal under analysis by maximizing the normalized cross-correlation between the mentioned signals. Optimized chemical shift values of the metabolites are obtained. This method, QM-QUEST, provides more robust fitting while limiting user involvement and respects the correct fingerprints of metabolites. Its efficiency is demonstrated by accurately quantitating 33 signals from tissue samples of human brains with oligodendroglioma, obtained at 11.7 tesla. The corresponding chemical shift changes of several metabolites within the series are also analyzed.

A theoretical investigation of the electronic structure of the NaK molecule including spin-orbit effects has been performed for the 34 Ω((+∕-)) states dissociating adiabatically into the limits up to Na(3s(2)S(1/2)) + K(3d(2)D(3/2)) from both an ab initio approach and a long-range model. Equilibrium distances, transition energies, harmonic frequencies as well as depths of wells and heights of humps are reported for all the states. Formulas for calculating the long-range energies for all the 0(+∕-), 1, 2, and 3 states under investigation are also displayed. They are expressed in terms of the C(n) (n = 6,8, ...) long-range coefficients and exchange integrals for the (2S+1)Λ((+)) parent states, available from literature. As present data could help experimentalists we make available extensive tables of energy values versus internuclear distances in our database at the web address: http://www-lasim.univ-lyon1.fr/spip.php?rubrique99.

1H Nuclear Magnetic Resonance (NMR) spin-Hamiltonian parameters: chemical shifts δ and spin–spin coupling constants J have been calculated using density functional theory, for the three polyamines: putrescine, spermidine and spermine present in prostate tissue. The Boltzmann weighted average of the chemical shifts and spin–spin coupling constants over a large number of stable conformers have been evaluated for each molecule. The comparison of such average chemical shifts with experimental values shows a significant improvement from values corresponding to the lowest-energy conformers, with rms errors of 0.15ppm for putrescine and 0.05ppm for both spermidine and spermine. From the comparison between spectra simulated from calculated δ and J parameters and experimental ones, the B3LYP/6-311++G** level of theory was seen to be a good compromise between accuracy and computational costs.

Chemical shifts δ have been calculated for the 1H attached to carbon atoms of sarcosine. Eight levels of theory within the DFT approach were used, mixing the four functionals B3LYP, PBE, OPBE, PBE0 and the two basis sets 6-311++G∗∗ and pcJ2. Boltzmann weighted isomer effects have been evaluated. By comparison of the 1H NMR spectrum simulated from the calculated δ and the experimental one that we acquired at 300MHz, the B3LYP/6-311++G∗∗ calculation was seen to be a good compromise between accuracy and cost. Zero-point vibrational corrections, estimated using a second-order perturbation approach, increase the agreement with experiment.

The aim of this work is to determine quantum mechanically the width Γ and the shift Δ of the lithium Li(2p→2s) and potassium K(4p→4s) resonance lines when these atoms are evolving in their parent gases. The interaction potentials along which the atoms Li(2p)+Li(2s) and K(4p)+K(4s) approach each other are constructed from reliable data. The radial wave equation is then solved numerically by using these potentials to compute the elastic phase shifts. By adopting the simplified Baranger model for the pressure broadening, which assumes the impact approximation, the cross sections effective in linewidth and lineshift are analyzed. The analysis leads in particular to the determination of the width and shift rates and the computations show that these rates have constant values and, mainly, do not depend on temperature. An approximate method is further applied to the calculations of the cross sections. The results reveal the influence of the long-range -C3/R3 interactions and confirm the universality of the obtained formulas of Γ and Δ.

A theoretical investigation of the electronic structure of the K-2 molecule, including spin-orbit effects, has been performed. Potential energies have been calculated over a large range of R up to 75a(0) for the 88 ((+/-))(g,u) states dissociating adiabatically into the limits up to K(4p P-2(3/2))+K(4p P-2(3/2)). Equilibrium distances, transition energies, harmonic frequencies, as well as depths for wells and heights for barriers are reported for all of the bound ((+/-))(g,u) states. Present ab initio calculations are shown to be able to reproduce quite accurately the small structures (wells and barrier) displayed at very long-range (R>50a(0)) by the (2,3)1(u) and (2)0(g)(-) purely long-range states. As the present data could help experimentalists, we make available extensive tables of energy values versus internuclear distances in our database at the web address http://www-lasim.univ-lyon1.fr/spip.php?rubrique99.

A theoretical investigation of the electronic structure of the K2 molecule, including spin-orbit effects, has been performed. Potential energies have been calculated over a large range of R up to 75a0 for the 88 Ωg,u(+/−) states dissociating adiabatically into the limits up to K(4p P23/2)+K(4p P23/2). Equilibrium distances, transition energies, harmonic frequencies, as well as depths for wells and heights for barriers are reported for all of the bound Ωg,u(+/−) states. Present ab initio calculations are shown to be able to reproduce quite accurately the small structures (wells and barrier) displayed at very long-range (R>50a0) by the (2,3)1u and (2)0g− purely long-range states. As the present data could help experimentalists, we make available extensive tables of energy values versus internuclear distances in our database at the web address http://www-lasim.univ-lyon1.fr/spip.php?rubrique99.