New insight into the low-energy 9^9He spectrum

The spectrum of $^9$He was studied by means of the $^8$He($d$,$p$)$^9$He reaction at a lab energy of 25 MeV/n and small center of mass (c.m.) angles. Energy and angular correlations were obtained for the $^9$He decay products by complete kinematical reconstruction. The data do not show narrow states at $\sim$1.3 and $\sim$2.4 MeV reported before for $^9$He. The lowest resonant state of $^9$He is found at about 2 MeV with a width of $\sim$2 MeV and is identified as $1/2^-$. The observed angular correlation pattern is uniquely explained by the interference of the $1/2^-$ resonance with a virtual state $1/2^+$ (limit on the scattering length is obtained as $a > -20$ fm), and with the $5/2^+$ resonance at energy $\geq 4.2$ MeV.Comment: 5 pages, 4 figures, 2 table

Предельные характеристики согласования приемных рамочных антенн с помощью нефостеровских цепей

The limiting characteristics of electrically small-sized loop antenna matching by means of non-Foster's negative inductance are studied. Various options for including negative inductance in frame antenna structure are considered. The analytical limit expression for the operating frequency band of the small-sized loop antenna with the inclusion of negative inductance in the gap of the conductor frame is obtained. It is shown that for practical implementation the most convenient is the scheme with the inclusion of negative inductance between the conducting plane and the free output of the frame. Such inclusion of negative inductance causes small loss in width of the working frequency band compared with the inclusion of this inductance in the gap of the frame conductive plane, but EMF induced in the frame is twice as large.  An integral expression is obtained for the maximum band matching of the small-sized loop antenna with the inclusion of negative inductance in grounded output, the integral in which is calculated numerically for various small-sized loop antenna quality factor and ratios between resonant frequency of the frame and operating frequency range. The results obtained are similar to Fano-Yula restriction for passive matching chains.Исследуются предельные характеристики согласования электрически малоразмерной рамочной антенны с помощью простейшей нефостеровской цепи – отрицательной индуктивности. Рассмотрены различные варианты включения отрицательной индуктивности в структуру рамочной антенны. Получено аналитическое предельное соотношение для рабочей полосы частот рамочной антенны при включении отрицательной индуктивности в разрыв проводника рамки. Показано, что для практической реализации наиболее удобной является схема с включением отрицательной индуктивности между проводящей плоскостью и свободным выводом рамки. При таком включении нефостеровского элемента существует небольшой проигрыш в ширине рабочей полосы частот по сравнению с включением этой индуктивности в разрыв проводящей плоскости рамки, однако в 2 раза выше наводимая в рамке ЭДС. Получено интегральное выражение для максимальной полосы согласования рамочной антенны при включении отрицательной индуктивности у заземленного вывода, интеграл в котором вычислялся численно для различных добротностей рамочной антенны и соотношений между резонансной частотой рамки и рабочим диапазоном частот. Полученные результаты подобны ограничению Фано–Юлы для пассивных согласующих цепей

Three-body correlations in direct reactions: Example of 6^{6}Be populated in (p,n)(p,n) reaction

The $^{6}$Be continuum states were populated in the charge-exchange reaction $^1$H($^{6}$Li,$^{6}$Be)$n$ collecting very high statistics data ($\sim 5 \times 10^6$ events) on the three-body $\alpha$+$p$+$p$ correlations. The $^{6}$Be excitation energy region below $\sim 3$ MeV is considered, where the data are dominated by contributions from the $0^+$ and $2^+$ states. It is demonstrated how the high-statistics few-body correlation data can be used to extract detailed information on the reaction mechanism. Such a derivation is based on the fact that highly spin-aligned states are typically populated in the direct reactions.Comment: submitted to Physical Review

10He low-lying states structure uncovered by correlations

The 0+ ground state of the 10He nucleus produced in the 3H(8He,p)10He reaction was found at about $2.1\pm0.2$ MeV (\Gamma ~ 2 MeV) above the three-body 8He+n+n breakup threshold. Angular correlations observed for 10He decay products show prominent interference patterns allowing to draw conclusions about the structure of low-energy excited states. We interpret the observed correlations as a coherent superposition of the broad 1- state having a maximum at energy 4-6 MeV and the 2+ state above 6 MeV, setting both on top of the 0+ state "tail". This anomalous level ordering indicates that the breakdown of the N=8 shell known in 12Be thus extends also to the 10He system.Comment: 5 pages, 5 figure

Alpha cluster resonance structure of light nuclei close to coulomb barrier

The aim of this experimental study is to investigate the structure of the 19F nuclei at energies representing astrophysical interest. Here we study the resonant interaction 15N+4He in the cyclotron DC-60 in Astana