Analysis of F and C NMR spectra of tetrafluorophthalic anhydride and its derivatives

¹⁹F and ¹³C NMR spectra of perfluorinated compounds (i.e., tetrafluorophthalic anhydride, its hydroxyl- and amino-derivatives, N-pentafluorophenyltetrafluorophthalimide, and hexafluoroindan-1,3-dione) were analysed. Different signals in NMR spectra were assigned based on the analysis of spin-spin coupling constants. All assignments made were further confirmed by density functional theory (DFT) calculations of ¹³C chemical shifts and J_C,F coupling constants.     

To the problem of numerical simulation of gas optical breakdown on GPU

An efficient solution for a key problem of implicit simulations of nonlinear interaction of ultra-short laser pulses with gaseous matter is proposed. The algorithm of fast tridiagonal linear system solver is discussed. The proposed implementation accounts for specific features of 2d data processing on GPU.     

Generation of higher harmonics for resonance oscillations in an open-ended pipe

We present a theory of resonance oscillations at doubled and tripled frequencies in a pipe open at one end. The boundary condition at the open end is obtained with allowance for the subharmonicity of speed fluctuations at the open end; it does not contain empirical parameters. Quite good qualitative and quantitative coincidence of the theoretical and experiment results is achieved.     

Plasma mechanisms of pulsed terahertz radiation generation

We present the results on generating terahertz radiation in the plasma of an optical discharge arising in the atmosphere during the focusing of femtosecond laser radiation. Different generation schemes related to focusing of the optical radiation by spherical and axicon lenses, with a constant electric field imposed on the laser spark region, as well as with the use of bichromatic laser radiation, are studied. Directivity patterns and polarization distributions of the terahertz radiation are analyzed in detail for different generation techniques. Comparison with the experimental results obtained by other research groups is given. Possible nonlinear mechanisms of the terahertz radiation generation are discussed.     

Inclusive two-particle correlations in 40 GeV/c π−p collisions and particle production mechanisms

Inclusive two-particle correlations in rapidity variables between π⁺π^?, π⁺π⁺ and π^?π^? obtained in 40 GeV π^?p collisions are discussed in the framework of the Mueller Regge model and the multiperipheral cluster model. The data show features similar to the data reported at much higher energies from the CERN ISR. This behaviour is more easily understood from the multiperipheral cluster model. Data on transverse momentum correlations in the same reactions can be qualitatively understood from the same model.