Spectrum quantum-mechanical calculation

Shaltout 1. and Mohamed T. A., Raman spectrum, quantum mechanical calculations and vibrational assignments of (95%-Te02 5% Sm203) glass, Spectrochim. Acta A Mol. Blomol. Spectros., 67,454 (2007). 

Phosphacarba- f6>-pentaborane [2-/Bu-l,2-PCB3Fl5] 25 was synthesized by gas-phase reaction of phosphaalkyne with tetraborane(lO) (see Figure 11). In the 31P NMR spectrum a signal at —501 ppm was detected for the apical phosphorus atom and confirmed by quantum mechanical calculations.120... 

The nitrosyldioxyl radical has largely been ignored in the chemical literature because it is relatively unstable in air. Nitrosyldioxyl radical is approximately 4.8 kcal/mol less stable than nitric oxide and oxygen in the gas phase less than 0.1% of the nitric oxide will combine with oxygen under standard conditions in the gas phase. Although present in low concentrations, the infrared spectrum of nitrosyldioxyl radical has been reported in the gas phase (Guillory and Johnston, 1965) and ab initio quantum mechanics calculations have been performed (Boehm and Lohr, 1989). 

Scandium phthalocyanine (H2pc) complexes have been obtained and quantum mechanical calculations carried out on these systems. Thus Sc(pc)Cl is obtained from reaction of ScCl3 with either phthalonitrile or with Li2(pc) and gives a molecular ion in the mass spectrum.29 The molecular orbitals of scandium (and other) phthalocyanines have been calculated and the electron distribution over the ring system studied in relation to the effect of the scandium ion.30... 

Le Quere and Leforestier (1990, 1991) calculated the autocorrelation function directly using the same PES and found fair agreement in regard of the recurrence times while the amplitudes were in remarkable disagreement. This may be due to either deficiencies of the calculated PES or the neglect of nonzero total angular momentum states in the theory. If the recurrences in the autocorrelation function are rescaled, the quantum mechanically calculated spectrum agrees well with experiment. 

The solid-state 13C cp/mas for crystalline 39, and the quantum mechanical calculated 13C chemical shifts and JHh coupling constants for a TBC model are listed in Table 15. Comparison of the 13C chemical shift values in the cp/mas spectrum versus corresponding values for those from the quantum mechanical calculation shows them to be similar. Dissolution of either quaternary ammonium salt in CDC13 solution affords two species (88 12) in which the major species has undergone a conformational change to a (reference,S)-TCBtype3 structure, while the... 

The radical cation of [ 1.1.1.1 Jisopagodane could be generated by y-UTadiation in a freon matrix. The corresponding EPR spectrum indicated two H hfc values, one of 0.95 (4 equivalent H) and one of 0.11 mT (4 equivalent H) showing that the D2d symmetry of the parent molecule was reduced to C2v This mirrors a slight ring extension but still a cyclobutanoid conhguration as confirmed by quantum mechanical calculations. 

The procedure of interpreting data concerning the molecule OPCl is described as an example. Fig. 4.4-3 shows the infrared spectrum of matrix-isolated OPCl with the two stretching vibrations at 1237.7 ( /(PO)) and at 489.4 cm (z/(PCl)). The deformation mode, of much lower intensity, lies at 308.0 cm. By using the precursor P OCl3, the absorptions are shifted to 1211.8, 484.7, and 298.0 cm respectively. These data confirmed the assignment of vibrations and the assumed sequence of the atoms O-P-Cl. Furthermore, by means of a normal coordinate analysis it was possible to limit the bond angle to a value of 105°, which is in accordance with the results of quantum-mechanical calculations. 

UV-vis spectrum of an analyte in solution is usually broad with very few narrow bands and shoulder. However, based on the nature of specific functional groups present in a molecule, some general spectral behavior was observed. Based on these studies and with the aid of quantum mechanical calculations, empirical relationships between structure and functional groups... 

The collinear model (Eq. (15)) has been successfully used in the semiclassical description of many bound and resonant states in the quantum mechanical spectrum of real helium [49-52] and plays an important role for the study of states of real helium in which both electrons are close to the continuum threshold [53, 54]. The quantum mechanical version of the spherical or s-wave model (Eq. (16)) describes the Isns bound states of real helium quite well [55]. The energy dependence of experimental total cross sections for electron impact ionization is reproduced qualitatively in the classical version of the s-wave model [56] and surprisingly well quantitatively in a quantum mechanical calculation [57]. The s-wave model is less realistic close to the break-up threshold = 0, where motion along the Wannier ridge, = T2, is important. 

In the photoelectron spectrum of O2, the bands corresponding to Ittu and 2change positions relative to each other (Fig. 6.10). This agrees with 2cTg lying substantially below ItTu, as found in quantum-mechanical calculations. 

It is generally observed for many polymers that the aggregation of the polymer chains leads to a spectral red-shift in their absorption spectra.11 Quantum mechanics calculations also suggest that a tt-tt stacking of the polymer backbones can red-shift the absorption spectrum.47 If this explanation also applies to MEH-PPV films, a spectral red-shift in the absorption spectrum is expected as the aggregation... 

A. Navarro, M. Femdndez-G6mez, J.J. L6pez-GonzdIez, M.P. Paz Femdndez-Liencres, E. Martinez-Torres, J. Tomkinson G.J. Kearley (1999). J. Phys. Chem. A. 103, 5833-5840. Inelastic neutron scattering spectrum and quantum mechanical calculations of the internal vibrations of pyrimidine. 

This additional energy content is attributed to an antiaromatic destabilization of the bicyclopentene ground state. The homoantiaromatic character of bicyclopentene has been postulated on the basis of quantum mechanical calculations (94) and has recently also been derived from the photoelectron spectrum (95). 

We have alluded to the connection between the molecular PES and the spectroscopic Hamiltonian. These are two very different representations of the molecular Hamiltonian, yet both are supposed to describe the same molecular dynamics. Furthermore, the PES often is obtained via ab initio quantum mechanical calculations while the spectroscopic Hamiltonian is most often obtained by an empirical fit to an experimental spectrum. Is there a direct link between these two seemingly very different ways of apprehending the molecular Hamiltonian and dynamics And if so, how consistent are these two distinct ways of viewing the molecule ... 

First consider a gas of spherical top molecules that is so dilute that intermolecular interactions can be ignored. Although the motions of the individual molecules are clearly quantized, we present here a classical calculation of the spectrum, leaving the quantum mechanical calculation as an exercise for the reader. 

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