Reaction cross sections (sigma(R)) for 19C, 20C and the drip-line nucleus 22C on a liquid hydrogen target have been measured at around 40A MeV by a transmission method. A large enhancement of sigma(R) for 22C compared to those for neighboring C isotopes was observed. Using a finite-range Glauber calculation under an optical-limit approximation the rms matter radius of 22C was deduced to be 5.4+/-0.9 fm. It does not follow the systematic behavior of radii in carbon isotopes with N < or = 14, suggesting a neutron halo. It was found by an analysis based on a few-body Glauber calculation that the two-valence neutrons in 22C preferentially occupy the 1s(1/2) orbital.

A new measurement of proton resonance scattering on 7 Be was performed up to the center-of-mass energy of 6.7 MeV using the low-energy RI beam facility CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study of the University of Tokyo. The excitation function of 7 Be+p elastic scattering above 3.5 MeV was measured successfully for the first time, providing important information about the resonance structure of the 8 B nucleus. The resonances are related to the reaction rate of 7 Be(p,γ) 8 B, which is the key reaction in solar 8 B neutrino production. Evidence for the presence of two negative parity states is presented. One of them is a 2 − state observed as a broad s-wave resonance, the existence of which had been questionable. Its possible effects on the determination of the astrophysical S-factor of 7 Be(p,γ) 8 B at solar energy are discussed. The other state had not been observed in previous measurements, and its J π was determined as 1 − .

The quadrupole collectivity of neutron-rich even-even neon and magnesium nuclei around N = 20, 28,30 Ne,and 32,34,36 Mg, was studied via proton inelastic scattering on a liquid hydrogen target by in-beam γ -ray spectroscopy in inverse kinematics. The angle-integrated cross sections for the first 2 + states of these nuclei were determined by measuring de-excitation γ rays. The deformation lengths were extracted from the angle-integrated cross sections using distorted-wave calculations. The deformation length of 30 Ne (δ (p,p ) = 1.59 +0.08 −0.09 fm) is smaller than that of 32 Mg (1.83 +0.10 −0.11 fm), which exhibits the largest quadrupole collectivity among the neutron-rich N = 20 isotones. Along the magnesium isotopic chain, the deformation lengths of 34 Mg and 36 Mg were deduced to be 2.30 +0.09 −0.10 fm and 1.90 +0.16 −0.17 fm, respectively. The evolution of quadrupole deformation in the vicinity of 32 Mg is discussed by comparing the present results with the theoretical calculations.

One and two-neutron removal-reactions from 19 C and 20 C have been studied using a liquid-hydrogen target at 40 A MeV. A small cross section has been observed in the one-neutron removal reaction from 20 C. The observed inclusive removal cross sections are compared with theoretical removal cross sections calculated by using shell model spectroscopic factors and Glauber-model single-particle cross-sections. The observed momentum distributions are also compared with those calculated by using continuum-discretized coupled-channel methods. Good consistency between theory and experiment is shown in the one-neutron removal reaction from 19 C. However, our theoretical calculation fails to reproduce the neutron removal reactions from 20 C, which suggests that further improvements of the theoretical descriptions are necessary.

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