Реакция фоторождения мезонов на нуклонах и ядрах в резонансной области энергий

Исследования реакции фоторождения мезонов на нуклонах необходимы для получения спектра возбужденных барионных резонансов. В данной работе исследуется кинематика реакции фоторождения на протоне каона и вычислены сечения в рамках изобарной модели этой реакции в области энергии возбуждения резонанса N(1900)3/2+ с помощью формулы Брейта-Вигнера для изолированного резонанса и мультипольного анализа. Полученные оценки сечения согласуются с имеющимися экспериментальными данными.Investigations of the photoproduction of mesons on nucleons are necessary for obtaining the spectrum of excited baryon resonances. In this paper, we study the kinematics of the photoproduction reaction on the proton of the kaon and calculate the cross sections in the framework of the isobar model of this reaction in the region of the excitation energy of resonance N (1900) 3/2 * using the Breit-Wigner formula for isolated resonance and multipole analysis. The obtained estimates of the cross section agree with the available experimental data

Electrical Properties of Unintentionally Doped Semi-Insulating and Conducting 6H-SiC

Temperature dependent Hall effect (TDH), low temperature photoluminescence (LTPL), secondary ion mass spectrometry (SIMS), optical admittance spectroscopy (OAS), and thermally stimulated current (TSC) measurements have been made on 6H-SiC grown by the physical vapor transport technique without intentional doping. n- and p-type as well semi-insulating samples were studied to explore the compensation mechanism in semi-insulating high purity SiC. Nitrogen and boron were found from TDH and SIMS measurements to be the dominant impurities that must be compensated to produce semi-insulating properties. The electrical activation energy of the semi-insulating sample determined from the dependence of the resistivity was 1.0 eV. LTPL lines near 1.00 and 1.34 eV, identified with the defects designated as UD-1 and UD-3, were observed in all three samples but the intensity of the UD-1 line was almost a factor of 10 more in the n-type sample than in the the p-type sample with that in the semi-insulating sample being intermediate between those two. OAS and TSC experiments confirmed the high purity of this material. The results suggest that the relative concentrations of a dominant deep level and nitrogen and boron impurities can explain the electrical properties in this material