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1.
First principles electronic structure calculations were carried out to determine the relative stabilities of the rutile- and CdI2-type structures of platinum dioxide (PtO2) and titanium dioxide (TiO2). The orbital interactions between the transition metal d- and oxygen p-orbitals were analyzed to gain insight into why PtO2 has both the rutile- and CdI2-type structures, but TiO2 has only the rutile-type structure. The cause for the large difference in the c/a ratios of the CdI2-type structures of TiO2 and PtO2 was examined. 相似文献
2.
C. Soulard P. Deniard S. Jobic M.-H. Whangbo 《Journal of solid state chemistry》2005,178(6):2008-2014
High-pressure X-ray diffraction measurements were carried out for polymeric CdI2-type compounds MTe2 (M=Pt, Pd) to investigate if they undergo a structural phase transition under pressure as does IrTe2. Up to 27 GPa at room temperature PtTe2 does not undergo any structural phase transition. In contrast, however, an abrupt change in the inter-atomic distances occurs in PdTe2 above 15.7 GPa at room temperature, and above 5 GPa at 300 °C, but the volume vs. pressure curve exhibits no discontinuity. To account for the differences between the isostructural compounds PtTe2, PdTe2 and IrTe2, their electronic structures and bonding were analyzed on the basis of first principles electronic band structure calculations. 相似文献
3.
Goubet M Asselin P Soulard P Lewerenz M Latajka Z 《The Journal of chemical physics》2004,121(16):7784-7794
Fourier transform infrared spectra of the nu(s) band of the (CH2)(2)S-DF complex have been recorded at 0.1-0.5 cm(-1) resolution in a cooled cell and in a supersonic jet expansion seeded with argon. A sufficient density of (CH(2))(2)S-DF heterodimers is produced by a double injection nozzle device, which limits the possibility of reaction between thiirane and DF before the expansion. The observation of partially resolved PQR branch structures at cell temperatures as high as 252 K indicates relatively small effective line widths, which allow a detailed analysis of the underlying vibrational couplings and of the structural properties of the complex. The analysis of cell and free jet spectra in the temperature range 50-250 K is performed with a software package for the simulation and fitting of multiple hot band progressions in asymmetric rotors. The analysis reveals that the three low frequency hydrogen-bond modes are strongly coupled to the DF stretch with anharmonic coupling constants, which indicates a strengthening of the hydrogen bond upon vibrational excitation of DF. Rovibrational parameters and a reliable upper bound for the homogeneous line width have been extracted. 相似文献
4.
G. H. Boldingh Gay Astruc A. Jaworowsky Schacherl H. Mühe Richard Firbas Morpurgo A. Alder Jahoda G. Vulpius M. G. Denigès Maquenne Taine Bocquillon Soulard Barnouvin und F. Wichlog 《Fresenius' Journal of Analytical Chemistry》1902,41(3-4):260-268
Ohne Zusammenfassung 相似文献
5.
Laser-induced fluorescence spectra for the first allowed electronic transition (22125 cm?1) of methylglyoxal (CH3COCHO) and its perdeutero analog (CD3COCDO) in a supersonic nozzle beam are quantitatively represented assuming that the potential function governing the CH3(CD3) rotation is changed during the transition. In the excited state the potential function is ternary (V1 = 95 (1 + cos 3θ)cm?1) as in the fundamental state (V0 = 134.5 (1 - cos 3θ)cm?1), but the minima are shifted by an angle of π/3. The spectrum of biacetyl (CH3COCH3CO) can be reproduced assuming two uncoupled methyl groups undergoing similar conformational changes during the electronic transition (the estimated potential function is V1 = 117.5 (1 + cos 3θ) cm?1 for each methyl group), in perfect agreement with the most recent assignment of the 0-0 transition. These results are consistent with ab initio calculations for the fundamental and first excited singlet states. 相似文献
6.
Soulard P Asselin P Cuisset A Aviles Moreno JR Huet TR Petitprez D Demaison J Freedman TB Cao X Nafie LA Crassous J 《Physical chemistry chemical physics : PCCP》2006,8(1):79-92
CHFClI is among the more favorable molecules for parity violation (PV) measurements in molecules. Despite the fact that calculated PV effects are two orders of magnitude smaller than in some organometallic compounds, CHFClI displays interesting features which could make possible a new experimental PV test on this molecule. Indeed, ultrahigh resolution spectroscopy using an ultrastable CO(2) laser is favored by several intrinsic properties of this molecule. For example, the high vapor pressure of CHFClI allows investigation by supersonic beam spectroscopy. Indeed, the spectroscopic constants have been accurately determined by microwave and millimetre wave spectroscopy. This is important for the subsequent selection of an appropriate absorption band of CHFClI that could be brought to co?ncide with the absorption of CO(2). Partially resolved (+)- and (-)-CHFClI enantiomers with respectively 63.3 and 20.5% ee's have been recently prepared and analyzed by molecular recognition using chiral hosts called cryptophanes. Finally, the S-(+)/R-(-) absolute configuration was ascertained by vibrational circular dichro?sm (VCD) in the gas phase. 相似文献
7.
B.?Xu P.?CamyEmail author J.?L.?Doualan R.?Soulard A.?Braud Z.?P.?Cai R.?Moncorgé 《Applied physics. B, Lasers and optics》2012,106(1):19-24
CW laser emission on the quasi 3-level (4F3/2→4I9/2) transition in Nd:GGG is reported for different pump focusing and resonator dimensions. A nearly hemispherical plano-concave
resonator led at 937.3 nm to a maximum output power of 4.1 W for an incident pump power of 21.7 W, thus corresponding to a
slope efficiency of about 23.5%. Laser operation was also obtained for the first time around 933.6 nm by using a glass etalon
for frequency selection with a maximum output power of 2.3 W and a slope efficiency of 16% with respect to the incident pump
power. Dual-wavelength operation (around 933.6 and 937.3 nm), which offers a potential source to generate THz radiation, is
also reported. 相似文献
8.
Summary Substituted β-cyclodextrin chiral stationary phases having different types of phenyl carbamate substituents have been prepared
and evaluated (retention, selectivity, resolution) for the liquid chromatographic separation of several series of enantiomers.
The influence on separations of the degree of substitution and the structure of the substituent are discussed. Different mechanisms
are suggested to explain separations in normal mode conditions. 相似文献
9.
The infrared OH-stretching band shape of crystalline formic acid (HCOOH) at low temperature is analyzed on the ground of a recent theory involving a semiclassical approximation for the evolution operator. The adiabatic potential function for the slow OO stretching mode (N coordinate) is computed from the observed spectrum for the excited state of the fast νOH vibration (n coordinate) and is compared with that derived from a time-independent approach. Both theories are consistent with Morse-type potentials and a large shortening of the hydrogen bond in the excited state. The dipole moment operator appears to be N independent. An additional coupling between n and an external OO bending coordinate of the hydrogen bond which manifests itself as a Franck—Condon progression of the νOH mode is introduced to account for the observed band manifold. The structure and the dynamics of formic acid in the ground and upper states of the νOH vibration are discussed and compared with those previously obtained for similar moderately strong hydrogen-bonded systems. 相似文献
10.
Asselin P Soulard P Madebène B Esmail Alikhani M Lewerenz M 《Physical chemistry chemical physics : PCCP》2006,8(15):1785-1793
The rotationally resolved infrared spectrum of the hydrogen bonded complex H(2)S-HF and of its isotopomer D(2)S-DF in the HF/DF stretching range have been observed in a supersonic jet Fourier-transform infrared (FTIR) experiment and indicate a predissociation lifetime of 130 ps for H(2)S-HF. Complementary spectra taken at a temperature of 190 K in a cell without resolved rotational structure indicate the presence of strong anharmonic couplings between low frequency intermolecular modes and the HF donor stretch mode previously observed in other complexes with heavier acceptor molecules without rotational fine structure. The anharmonic analysis of the hot band progressions and of the rotational data confirm the coupling mechanism. The coupling constants and the absolute frequency of the hydrogen bonded stretch mode are in excellent agreement with theoretical predictions based on adiabatic variational calculations on potential surfaces computed at MP2 and CCSD(T) level. Complementary calculations with a perturbational approach further confirm the coupling model. 相似文献