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Spectroscopic Parameters (spectroscopic + parameter)

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Chemistry80%

Selected Abstracts

Synthesis and Conformational Analysis of Tetrahydroisoquinoline-Fused 1,3,2-Oxazaphospholidines and 1,2,3-Oxathiazol­idines

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2008
Ildikó Schuster
Abstract The cyclizations of tetrahydroisoquinoline 1,2-amino alcohols with phenylphosphonic dichloride, bis(2-chloroethyl)phosphoramidic dichloride, thionyl chloride and sulfuryl chloride were utilized to synthesize 1,5,6,10b-tetrahydro-1,3,2-oxazaphospholo[4,3- a]isoquinolines (2, 3), 1,5,10,10a-tetrahydro-1,3,2-oxazaphospholo[3,4- b]isoquinolines (8, 9), 1,5,6,10b-tetrahydro-1,2,3-oxathiazolo[4,3- a]isoquinolines (4,6) anda 1,5,10,10a-tetrahydro-1,2,3-oxathiazolo[3,4- b]isoquinoline (11), which are the first representatives of these ring systems. NMR spectroscopic analysis revealed the existence of conformational equilibria that are fast on the NMR timescale. Theoretical DFT calculations pointed to the participation of generally two preferred conformers in the conformational equilibria; the positions of the equilibria were indicated by the experimental NMR spectroscopic parameters, and they are in good agreement with the theoretically calculated energy differences of the participating conformers. For two compounds, which could be not isolated (10, 12), both the preferred conformers and the stereochemistry could be concluded from the DFT calculation results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Theoretical investigations on analytical potential energy function and spectroscopic parameters for the state b3,u of dimer 7Li2

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2007
De-Heng Shi
Abstract The SAC-CI (symmetry-adapted-cluster configuration-interaction) method presented in Gaussian 03 program package is applied to investigate the adiabatic potential energy curves (PECs) of 7Li2(b3,u). These calculations are performed at numbers of basis sets, such as 6-311++G(3df,3pd), 6-311++G(2df,2pd), 6-311++G(df,pd), D95V++, D95(3df,3pd), D95(d,p), cc-PVTZ, 6-311++G and 6-311++G(d,p). All the ab initio calculated points are fitted to the analytic Murrell-Sorbie functions and then used to compute the spectroscopic parameters. The analytic potential energy function (APEF) for this b3,u state is reported. By comparison, the spectroscopic parameters reproduced by the APEF attained at 6-311++G(2df,2pd) are found to be very close to the latest experimental findings. With the APEF obtained at the SAC-CI/6-311++G(2df,2pd) level of theory, a total of 62 vibrational states is found when J = 0. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants for these vibrational states are also reported. The reasonable dissociation limit for this state is deduced using the calculated results at present. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]

Intruder state avoidance multireference Møller,Plesset perturbation theory

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2002
Henryk A. Witek
Abstract A new perturbation approach is proposed that enhances the low-order, perturbative convergence by modifying the zeroth-order Hamiltonian in a manner that enlarges any small-energy denominators that may otherwise appear in the perturbative expansion. This intruder state avoidance (ISA) method can be used in conjunction with any perturbative approach, but is most applicable to cases where small energy denominators arise from orthogonal-space states,so-called intruder states,that should, under normal circumstances, make a negligible contribution to the target state of interests. This ISA method is used with multireference Møller,Plesset (MRMP) perturbation theory on potential energy curves that are otherwise plagued by singularities when treated with (conventional) MRMP; calculation are performed on the 13, state of O2; and the 21,, 31,, 23,, and 33, states of AgH. This approach is also applied to other calculations where MRMP is influenced by intruder states; calculations are performed on the 3,u state of N2, the 3, state of CO, and the 21A, state of formamide. A number of calculations are also performed to illustrate that this approach has little or no effect on MRMP when intruder states are not present in perturbative calculations; vertical excitation energies are computed for the low-lying states of N2, C2, CO, formamide, and benzene; the adiabatic 1A1,3B1 energy separation in CH2, and the spectroscopic parameters of O2 are also calculated. Vertical excitation energies are also performed on the Q and B bands states of free-base, chlorin, and zinc,chlorin porphyrin, where somewhat larger couplings exists, and,as anticipated,a larger deviation is found between MRMP and ISA-MRMP. © 2002 Wiley Periodicals, Inc. J Comput Chem 10: 957,965, 2002 [source]

Nonlinear refractive index of ceramic laser media and perspectives of their usage in a high-power laser-driver

LASER PHYSICS LETTERS, Issue 10 2004
Yu. Senatsky
Abstract At the recent years a technology of ceramic laser media on the base of crystals with a cubic symmetry has been developed. The perspective of the usage of ceramic materials in many different applications including high - power short pulse lasers stimulates the work on the systematic study of the properties of these new laser media. A nonlinear refractive index, n2 was studied for several garnet and sesquioxide laser ceramics using Z-scan method. n2 indices in the range of (2 , 6) × 10,13 were measured for YAG, Y2O3, Lu2O3, and Sc2O3 ceramic samples. These data together with the other laser and spectroscopic parameters of several Nd3+ and Yb3+ doped crystals of a cubic symmetry were used to estimate the properties of laser ceramics for the application in a high-power pulsed-repetitive laser - driver for inertial confinement fusion (ICF) program. A high heat conductivity of ceramic materials is a profitable characteristic for this application as compared to glasses, which are used now for experiments in ICF at single shots regime. Compared to single crystals, ceramic elements provide laser designers with a variety of new design options for the projects of laser-drivers. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]