On21Na states betweenE x=5.5 and 6.2 MeV

The wave functions of pionic atoms are obtained by numerical integration of the Klein-Gordon equation with the Kisslinger-Ericson potential. They are then approximated by two analytic expressions, one inside and the other outside the nuclear radius.     

15N(p,po)15N and the levels of 16O for Ex = 14.8–18.6 MeV

Angular distributions of cross section and analyzing power for elastic scattering of protons from ¹⁵N have been measured for E_p = 2.7–7.0 MeV. A phase-shift analysis of the data yields spin-parity assignments and level parameters for seventeen states of ¹⁶O in the excitation energy region 14.8–18.6MeV. Three of the resonances have not previously been identified, among them being a broad J^π = 2^? level at E_p = 6.1 MeV which is almost certainly the analog of the 2^? 1p1h state with configuration ($\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{,}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}$) at E_x ∽ 5.0 MeV in ¹⁶N. The broad level previously reported near E_p = 5.0 MeV has been observed and its parameters determined. A resonance analysis of the phase shifts yielded values of E_r, Γ and Γ_p for all of the levels. The J^π assignments are in agreement with previously reported values. For resonances having J = l, the data can usually be fit with a resonant phase shift corresponding to either J = l + 1 or J = l ? 1, in addition to the phase shift for J = l. Which of the two spurious-J solutions occurs seems to depend on whether the partial wave through which the resonant state is formed is $\text{J = l +}\text{1}\text{2}\text{or}\text{J = l ?}\text{1}\text{2}$.     

Lifetime of the 6793-keV state in 15O

The energy derived from the CN cycle at low stellar temperatures is regulated by the 14N(p,gamma)15O reaction. A previous direct measurement of this reaction has been interpreted as showing evidence for a subthreshold resonance which makes a major contribution to the reaction rate at low temperatures. This resonance, at E(c.m.) = -504 keV would correspond to the known Ex = 6793-keV state in 15O. We have measured a mean lifetime of 1.60(+0.75)(-0.72) fs (90% C.L.) for this state using the Doppler-shift attenuation method. This lifetime is a factor of 15 longer than that inferred from the (p,gamma) data and implies that the contribution of the subthreshold resonance is negligible.     

On the resonant behavior of the16O+15N reaction

The ¹⁶ O+ ¹⁵ N reaction products have been studied by the γ-ray detection method in the CM energy range 15.5 to 36.1 MeV and by the kinematical coincidence method at energies ranging from E _CM =20.6 to 33.5MeV. The γ-ray yield excitation function of the ¹⁶O 3^? inelastic channel shows the existence of resonant structures. Two structures with ～ 1.6 MeV width are observed in the large angle elastic scattering excitation function, they are correlated with the resonances seen in the inelastic channel. Angular momentum assignments were made from the elastic backward angular distributions.     

ft asymmetry in A = 12 mirror decay to the 12C 4.4 MeV state

The ratio of the Gamow-Teller beta-decay branches of ¹²B and ¹²N to the first excited state of ¹²C was measured accurately by means of the off-beam β-γ spectroscopy. The ratio of these branches was obtained as ¹²N/¹²B = 1.528 (27). This gives the mirror asymmetry [(ft)_β⁺/(ft)_β⁻]− 1 = 0.066 (18). The present value together with that for the ground-state decay is discussed in terms of the different radial overlapping.     

Existence of an α-decaying state of12C at Eexc=30.3 MeV

New results together with previous evidence are presented supporting the existence of a narrow state of¹²C at E_exc=30.3 MeV.     

Magnetic ordering in FexMg1−xCl2, (x=0.55, x=0.45, x=0.30)

Mössbauer measurements on the diluted crystals Fe_xMg_1–xCl₂ show that fluctuating magnetic clusters are present. These can be related to the known spin-glass properties of these compounds. The fluctuating frequencies depend on temperature and the fluctuations can be suppressed by a sufficiently high external magnetic field     

The polarization of the neutrons from the reaction15N(d,n 0)16O atE d=4.35 and 5.50 MeV

In the reaction¹⁵N(d, n ₀)¹⁶O the angular dependence of the neutron polarization and of the differential cross section was measured at average deuteron energies of 4.35 and 5.50 MeV. Parallel features are observed.     

Two-neutron halo state of ~(15)B around 3.48 MeV by a three-body model

We investigate low-lying bound states of the neutron-rich nucleus ~(15)B by assuming it is a three-body system made of an inert core 13 B and two valence neutrons. The three-body wave functions are obtained using the Faddeev formalism. Special attention is paid to the excited state at 3.48(6) MeV observed in the 13 C(14 C,12 N)15 B reaction, whose properties are less clear theoretically. In our three-body model, besides the ground state 3/21, a second 3/2_2~-state is discovered at around 3.61 MeV, which might be identified with the excited state observed at3.48(6) MeV. We study this 3/2_2~-state in detail. It turns out to be a two-neutron halo state with a large matter radius r_m≈4.770 fm.     

The reactions 18O(p,p)18O and 18O(p,p')18O1(1.98 MeV) for Ep = 3.8–6.1 MeV

Angular distributions of cross sections and analyzing powers have been measured for ¹⁸O(p, p)¹⁸O and ¹⁸O(p, p₁)¹⁸O¹ (1.98 MeV) in 25 keV intervals for proton energies between 3.8 and 6.1 MeV. A phase-shift analysis of the elastic scattering data was carried out, yielding resonance parameters for 16 levels in ¹⁹F in the excitation energy region 11.6–13.8 MeV. The results generally are in good agreement with previous work. On the basis of spin, parity, excitation energy and a comparison of reduced proton widths with reduced neutron widths of levels in ¹⁹O, an assignment of $\text{T =}\text{3}\text{2}$ could be made to at least five of the levels, including the analog of the broad $\text{3}\text{2}{}^{\mathrm{+}}$ level in ¹⁹O at 5.45 MeV. A Legendre-polynomial analysis of the inelastic scattering data suggests that the cross section for proton energies between 5.0 and 5.5 MeV is dominated by the broad $\text{3}\text{2}$⁺ resonance at E_p = 5.15 MeV.     

Electromagnetic radiation of MeV electrons in thick aligned single crystals

Abstract

Earlier published theoretical models for MeV electrons are generalized in this paper. Different theoretical predictions for planar channeling and accompanying electromagnetic radiation in thick crystals are presented. A comparative analysis of theoretical and experimental spectra of photon radiation is given. Thickness dependences of channeling quantum state populations, radiation line broadening and photon flux intensities are obtained. The existence of planar electron channeling at 54 MeV in a silicon single crystal with a thickness of several millimetres is shown.     

Magnetic microstructure of strontium-substituted thulium ferromanganites Tm0.65Sr0.35Mn1 ? x Fe x O3 (x = 0.3?0.4)

The structural and magnetic properties of the Tm_0.65Sr_0.35Mn_{1 ? x} Fe _x O₃ (x = 0.3?0.4) have been studied by methods of magnetic resonance and differential thermomagnetic analysis. A magnetic phase separation has been revealed in structurally single-phase samples.     

18O(p,p)18O and18O(p,p′)18O1for E = 6.1−16.6 MeV

Angular distributions of cross sections and analyzing powers have been measured for ¹⁸O(p, p)¹⁸O and ¹⁸O(p, p₁)¹⁸O¹(1.98 MeV) for proton energies between 6.1 and 16.6 MeV. The measurement were crarried out in 25 keV intervals between 6.1 and 8.0 MeV, and in 100 keV intervals between 8.0 and 16.6 MeV. Although the general appearance of the angular distributions changes quite smoothly with energy above about 8 MeV, structure is evident in the backangle excitation functions up to 14 MeV. A phase-shift analysis of the elastic scattering data yielded resonance parameters for 25 levels in ¹⁹F in the excitation enrgy region 13.8?21.4 MeV. A large fraction of these levels have odd parity, and the energies of the $\text{1}\text{2}{}^{\mathrm{?}}$ and $\text{3}\text{2}{}^{\mathrm{?}}$ levels coincide closely with peaks seen in the ¹⁹F photonuclear yield curves. A simple model involving proton single-particle states coupled to the 2₁^+; and 3₁^? levels of ¹⁸O is able to account for some features of the observed structure. The energy-averaged elastic and inelastic scattering data for E_p > 12 MeV agree reasonably well with the spherical optical model and the DWBA, respectively, as well as with coupled-channels calculations.