Collisional parameters of N2 broadened methane lines in the R9 multiplet of the 2ν3 band. Multispectrum fittings of the overlapping spectral lines

A high-sensitive two-channel photo-acoustic (PA) spectrometer with a near infrared diode laser was used to make precise measurements of N₂-broadened methane spectra in the R9 multiplet of 2ν₃ band. For the accurate retrieval of spectroscopic line parameters (intensities, positions at zero pressure, pressure-shifting and -broadening, collisional narrowing and line mixing coefficients) from the methane PA spectra, a program based on a multispectrum fitting procedure has been used. The multispectrum least squares fitting procedure is based on a relatively simple line profile model and on the linear pressure dependences of the line profile parameters. The line parameters were determined for 11 lines of the methane 2ν₃ R9 multiplet. The results have been compared with other available data.     

First synthesis of totally orthogonal protected alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines.

The first synthesis of a series of totally orthogonal protected racemic alpha-(trifluoromethyl)- and alpha-(difluoromethyl)arginines is described. The key steps of the synthesis are the mild guanidinylation procedure and the selective hydrogenation of a CC triple bond in the presence of a Cbz-group.     

Energy spectrum of (Sn0.65Pb0.35)0.95Ge0.05Te solid solutions

The paper reports the study on the resistivity ρ and thermoemf S of the (Sn_0.65Pb_0.35)_0.95Ge_0.05Te solid solution layers. The dependences of ρ and S on the hole concentrations in the range 3×10¹⁹–2×10²¹ cm^?3 exhibit jumps in the resistivity and thermoemf minima at close hole concentrations p ₁≈9×10¹⁹ cm^?3, p ₂≈2.5×10²⁰ cm^?3, and p ₃≈4.5×10²⁰ cm^?3. The observed jumps and minima suggest a complex structure of the valence band and the presence of critical points in the energy spectrum of holes. According to the data for SnTe, the critical points in the energy spectrum at the given hole concentrations are identified as the Σ-extremum, saddle point LΣ, and Δ-extremum, respectively.     

Self-organization in the formation of a nanoporous carbon material

A new mechanism of nanopore formation in carbon materials produced by the interaction of car-bides with chlorine is proposed. In essence, this method is the following. A series of nonlinear chemical reactions proceed in the course of a chemical interaction between chlorine and a carbide. If the external parameters, the component fluxes, and the diffusion rates satisfy certain relations, the self-organization process can occur. This process results in the creation of a periodic nanoporous structure in the carbon material formed. A mathematical model is proposed, the main characteristics of the process are calculated, and the restrictions on the parameters at which the formation of the porous structure becomes possible are found.     

Stochastic resonance in a nonequilibrium electron-hole plasma

A photogenerated electron-hole plasma, heated in the process of Auger recombination, is studied. It is shown that in the plasma near the threshold for the appearance of uniform relaxational self-excited oscillations, weak noise transforms into a stochastic sequence of large-amplitude spikes. An additional optical periodic signal with amplitude approximately five times smaller than the noise variance, depending on the form of this signal, transforms these stochastic oscillations into low-amplitude quasiharmonic oscillations or into periodic spike self-excited oscillations of enormous amplitude. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 7, 422–427 (10 October 1999)