The pure rotational Raman spectrum of cyclopropane was observed up to J = 43. We have taken into account the effects of the unresolved K structure of the lines by assigning an effective value of K to the center of each unresolved line. Methods are developed for calculating effective K values for each value of J that allow a simultaneous fit to the R-and S-branch lines. The rotational constants of cyclopropane derived from this research are, in wavenumber units (cm?1); B0 = 0.67028, DJ = 1.0 × 10?6, and DJK = ?1.3 × 10?6. We have also tested the validity of the method by using it with recent Raman data for BF3. 相似文献
Methyl tunnel frequencies, measured at 4 K, are found to be 455 +/- 8 kHz in methyl malonamide and 496 +/- 8 kHz in methyl ethyl ketone. The first is unaffected by deuteration of the amide groups. Measurements of the temperature dependence of the spin lattice relaxation time are also reported for methyl malonamide and a further test is made of a previously reported correlation between tunnel frequency and the temperature of the T1 minimum. The measurements are in good agreement with the universal correlation curve. 相似文献
A theoretical explanation is proposed for the effect of variations in concentration of water molecule spin isomers in the gas phase during the interaction of molecules with a solid adsorbent surface. The explanation is based on antisymmetric (AS) correlation between proton spin moments and molecule rotation. A new AS correlation occurs during the interaction of the molecule with a dc electric field near the surface. Due to the new (external) AS correlation, ortho-and parawater molecules are formed; separation into spin modifications occurs over degenerate states of each rotational level of the molecule. Water molecule separation into spin modifications at the previous (internal) AS correlation occurs over rotational levels of molecules. The ratio of ortho-and parawater concentrations in the gas phase at the external AS correlation is compared with experimental data on chromatographic separation of water spin isomers. Quantitative agreement is observed between the calculated ratio and the ratio measured for water molecules at the final separation stage. 相似文献
We demonstrate collinear generation of equidistant rotational sidebands in low-pressure molecular hydrogen with near-unity conversion efficiency. The spectrum consists of 37 coherent sidebands covering over 20, 000 cm(-1) of spectral bandwidth and ranging from 1.37mum to 352 nm in wavelength. 相似文献
We report measurements of rotational Raman gain suppression in H2 in the transient regime. Quantitative information about the dependence of the amount of the gain suppression on the pump energy and the propagation angle relative to the pump beam is obtained from angularly resolved measurements of the small signal amplification. These measurements, along with qualitative observations of the Stokes spatial distribution under gain conditions, demonstrate that the gain suppression is confined to a narrow region around the phase matching angle for collimated beams with relatively low gain per unit length. For focused beams with higher gain per unit length the suppressed region can extend to the forward direction, resulting in a two- to three-fold estimated increase in the Raman threshold. 相似文献
The influence of the ellipticity degree of the pump radiation polarization on threshold energies and energy conversion efficiencies
of stimulated rotational Raman scattering (SRRS) are investigated in H2 with a XeCl excimer laser, by using different focusing geometries. For the first time, it is shown that the dependence of
SRRS on pump radiation polarization is also affected by the focusing geometry, i.e. whether low- or high-angle focusing is
applied. The experimentally determined threshold energies as a function of the pump radiation polarization are in accordance
with theory mainly at high-angle focusing geometries. It is also shown for the first time that gain suppression effects on
vibrational Raman scattering have to be considered in understanding the experimental results.
Received: 5 January 1999 / Final version: 10 September 1999 / Published online: 8 March 2000 相似文献
Abstract The rotational Raman spectra of four vapor phase isotopic methanols, CH3OH, CH3OD, CD3OH and CD3OD, have been reported for the first time in the wavenumber regions from 5 to 100–120 cm?1. The major parts of the spectra consist of bands equispaced at 3.19, 3.04, 2.56 and 2.46 cm?1 intervals, respectively, and have been interpreted as the pure rotational S-branch transitions. 相似文献
Two-channel lidar signals that are composed of total rotational scattering and elastic signals provide good information about aerosol scattering coefficients. We can calculate the aerosol backscattering coefficient and extinction coefficient directly, without making any assumption or calibration. Generally, a high-spectral-resolution lidar is used for aerosol monitoring, but we have designed a new low-spectral-resolution lidar system that contains both kinds of scattering information simultaneously, and we have retrieved the aerosol scattering coefficient. The results show that there is no need to assume any relation between aerosol backscattering and extinction or to consider any wavelength calibration to determine the aerosol scattering coefficient. 相似文献
Journal of Experimental and Theoretical Physics - The theory of multifrequency stimulated Raman scattering (SRS) of light on rotational transitions of molecules, which are simulated by a... 相似文献
The spatiotemporal effects generated in the wake of a laser filament propagating in nitrogen are investigated. At suitable time delays, a probe light pulse propagating along the wake experiences a strong spatial confinement and a noticeable spectral broadening at the same time. Numerical simulations, well reproducing the experimental findings, show the key role of the impulsive rotational Raman response in the observed phenomena. 相似文献
In previous publications [1–3], we have been concerned with the influence of hydrogen bond formation on the Raman intensity of the carbonyl stretching vibration. It has been shown that hydrogen bond association of simple carbonyl bases (cyclohexanone, acetone, acetophenone) with proton donors such as phenol derivatives, hydrochlorid or hydrobromic acid brings about an intensity increase of the νCO Raman band; moreover, the intensity enhancement is linearly related to the enthalpy of complex formation. In the present work, these measurements are extended to the complexes formed between methyl acetate (MeAc) and phenol derivatives. As suggested by the frequency lowering of the νCO vibration and the frequency increase of the νCO band, complex formation in solution takes place on the carbonyl function.From NMR [4–5] and UV data [6] it can also be concluded that protonation via hydrogen-bonded attachment occurs in solution predominantly at the carbonyl oxygen atom.Literature data for the thermodynamic quantities referring to esters with hydroxylic compounds are scarce. Consequently in this work, we have determined the equilibrium constants and the enthalpy of formation for complexes between MeAc and phenol derivatives. We also report the absolute intensity of the νCO Raman band in the free ester molecule and in the complexes, all measurements been made in a solvent of low polarity : carbontetrachloride. 相似文献
We report the use of silver (Ag) colloids in the spectroscopic differentiation of methyl red (MR) isomers (o-MR, m-MR, p-MR) by fluorescence techniques. Under different pH conditions, the formation of MR-Ag complex has an impact on the fluorescence band shapes and peak position shift, which are distinctive between MR isomers. The fluorescence quenching between 400 and 414 nm accompanied by simultaneous enhancement between 510 and 541 nm changes with pH are closely related to energy transfer efficiency and the interaction between the MR isomers and the Ag surface. 相似文献
It is our goal to obtain a reliable prediction of the rotational tunnelling spectrum to be expected for a long chain of coupled one-dimensional quantum rotors. The problem is intractable by the simple methods used so far for up to three coupled methyl groups. Therefore, an efficient, nevertheless sufficiently precise method for solving the stationary Schrödinger equation of interacting methyl groups is developed first; it proves to be valid for a broad range of not too weak potential strengths. Then, three scenarios are investigated: they differ with respect to the relative strength of the single-rotor potential and the interaction potential. For each scenario, we illustrate the dependence of the energy level scheme on the number of coupled groups. For strong coupling and weak single-particle potential, the characteristic features of the energy level scheme of interacting methyls are most clearly observable: For as few as four coupled methyl groups we predict tunnelling spectra which are hardly distinguishable from single-methyl spectra. However, the collective behaviour is still important for the value of the tunnelling splitting. Therefore, the interpretation of such a spectrum in terms of single-methyl tunnelling is obvious but misleading with respect to the potential seen by a methyl group in the crystal. 相似文献