Measurements of the fusion cross sections in the barrier and subbarrier regions are presented for the four heavy-ion systems ${}_{}{}^{46,50}{}_{}{}^{}\mathrm{Ti}$${+}^{90}$Zr${,}^{93}$Nb. The measured cross sections varied from 0.04 to 400 mb. The evaporation residues were detected by the use of a velocity filter. Procedures are described for extracting fusion cross sections from such measurements. The observed differences in the subbarrier fusion cross sections for the ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{93}{}_{}{}^{}\mathrm{Nb}$ nuclei, both of which have small collectivity, have led us to question the view that excursions of the strong nuclear force due to collective motions of the colliding nuclei are the primary enhancement mechanisms for the observed heavy-ion subbarrier fusion cross sections.

A simple formula is presented, based on a flat distribution of barriers, which is applied to the near-barrier region (10–200 mb). This formula states that the quantity (σE${)}^{1/2}$ vs E is linear in the near-barrier region with a zero intercept defining a threshold energy for fusion. These threshold values reflect variations in the binding energies of the valence neutrons. We also point out that the far-subbarrier region (<10 mb) shows large variations in fusion cross sections and that these variations reflect differences in the collectivities of the colliding nuclei (especially noticeable differences are seen between permanently deformed nuclei and ‘‘vibrational’’ nuclei). These systematics of heavy-ion subbarier fusion suggest that neck formation is playing an important role. The barrier for neutron transfer vanishes at distances typically 1.5 fm beyond the typical barrier distance and this distance could vary with the binding energy of the valence neutrons. The presence of neutrons in the region between the nuclei could promote neck formation which provides a force strong enough to overcome the Coulomb force. The collective properties of the colliding nuclei are then interpreted as a modulation of the threshold for neck formation and thereby reflect the large observed differences in the far-subbarrier cross sections. Formulas are presented for ${\mathrm{\sigma }}_{\mathit{L}}$ which result from a flat distribution of barriers. These formulas predict a broad bell-shaped spin distribution and are compared to the measured distribution in the subbarrier region for the system ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$${+}^{100}$Mo.

The feeding and decay patterns of isomers in odd-odd iodine nuclei, produced in heavy-ion fusion-evaporation reactions and separated by a recoil mass spectrometer, have been studied with the γ-ray spectroscopy technique. A new isomer in ${}_{}{}^{116}{}_{}{}^{}\mathrm{I}$, fed by a known collective band, was identified and its half-life was measured to be 3.27±0.16 μs. An isomer was confirmed to exist in ${}_{}{}^{122}{}_{}{}^{}\mathrm{I}$ with a measured half-life of 80±8 μs in agreement with two previous determinations. It is established from our study that these isomers serve as links between the high-spin and low-spin states in ${}_{}{}^{116,122}{}_{}{}^{}\mathrm{I}$. The characteristic properties of low excitation energy and high spin of these isomers are evident. As a by-product in the study of ${}_{}{}^{122}{}_{}{}^{}\mathrm{I}$, the half-life of a known high-spin isomer in ${}_{}{}^{121}{}_{}{}^{}\mathrm{I}$ was measured to be 16.0±1.4 μs, which disagrees with an early measurement of 9.0±1.5 μs. Its isomeric transition has an energy of 135 keV as suggested by our data in contrast to the value of 159 keV reported earlier.

Angular correlation measurements between heavy residues (${\mathit{Z}}_{\mathit{R}}$=23–13) and light fragments (${\mathit{Z}}_{\mathit{L}}$=2–10) have been performed for the reaction ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{26}$Mg at ${\mathit{E}}_{\mathrm{lab}}$=163.5 MeV. The binary nature of the mechanisms competing with fusion-evaporation is evidenced. Linear momentum analysis and velocity plots indicate contributions of binary reactions also for those elements that are generally believed to be produced by fusion-evaporation mechanisms.

A simple closed-form analytic expression for the heavy-ion reaction cross section, involving nuclear densities of colliding ions and the nucleon-nucleon cross section, has been obtained within the framework of the Glauber model modified for the Coulomb field effect. Reaction cross sections for a large number of heavy-ion systems have been predicted reasonably well over an energy range beginning with the Coulomb barrier to a few GeV/nucleon.

The coincident electrofission (e,e’f) cross sections of ${}_{}{}^{233,238}{}_{}{}^{}\mathrm{U}$ were measured in the excitation range 150–550 MeV. The probability of fission was found to be near unity in the delta resonance region (250–550 MeV), but less than unity in the quasifree scattering region (150–250 MeV). The data are analyzed with a model based on the quasifree and delta reaction mechanisms. An excitation energy of 25 MeV is found for the residual nucleus in the quasifree region and over 40 MeV in the delta region.

Reported are measurements of angular distributions of resonance-energy positive and negative pions exciting approximately 40 states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$. These include the (ground state, $0^{+}$), (1.36 MeV, $2^{+}$), (4.14, $2^{+}$), (5.93, $4^{+}$), (6.44, $0^{+}$), (7.34), (7.55, $3^{\mathrm{-}}$), (8.33, $3^{\mathrm{-}}$), (9.32, $4^{+}$), (9.97, $5^{\mathrm{-}}$), (11.08, $3^{\mathrm{-}}$), (12.06), (13.26), (13.96, $3^{\mathrm{-}}$), (15.1, T=1, $6^{\mathrm{-}}$), and (15.4) states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and the (ground state, $0^{+}$), (1.81, $2^{+}$), (2.92, $2^{+}$), (3.59, $0^{+}$), (4.31, $2^{+}$+$4^{+}$), (4.90, $4^{+}$), (5.31, $2^{+}$), (5.44, $4^{+}$), (5.69, $4^{+}$), (6.86, $3^{\mathrm{-}}$), (7.33, $3^{\mathrm{-}}$), (7.79, $3^{\mathrm{-}}$), (8.17, $3^{\mathrm{-}}$), (9.2, possible $6^{\mathrm{-}}$), (10.30, $4^{+}$), and (18.1, T=2, $6^{\mathrm{-}}$) states in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$. The distorted-wave impulse approximation with a Kisslinger form for the optical potential using a π-nucleon t matrix at a shifted energy of -25 MeV was found to explain the elastic scattering data from ${}_{}{}^{24,26}{}_{}{}^{}\mathrm{Mg}$ in the energy range 116–292 MeV that is spanned by these data. Inelastic distorted-wave impulse approximation calculations employing collective-model deformation parameters were simultaneously fitted to the ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ data for each state.

The deformation parameters and matrix elements in most cases compare favorably with results from other studies. Published s-d shell-model calculations using one value for the effective charges were found to reproduce the trend of both the strengths and ratios of neutron-to-proton matrix elements for the $2^{+}$ and $4^{+}$ states. The data at the first maximum in the inelastic angular distributions for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and that from other studies for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ show that the cross section for ${\mathrm{\pi }}^{+}$ scattering is equal to that for ${\mathrm{\pi }}^{\mathrm{-}}$ scattering, which forces the proton deformation parameters to be greater than the neutron deformation parameters and gives a ratio of neutron-to-proton elements to be less than unity. This difference from unity is interpreted as a measure of the failure of the model and a systematic error of 11% is assumed to dominate the errors in the results for ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$. Coupled-channels calculations employing monopole form factors are compared to data for low-lying $0^{+}$ states in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$.

For hadron-nucleus scattering, the projectile’s Coulomb interaction induces, in optical potential approximations to multiple-scattering theories, an effective shift in the local energy at which the optical potential is evaluated. In addition, it gives rise to a contribution related to the Coulomb excitation (or deexcitation) of the target accompanied by the corresponding deexcitation (or excitation) by the strong interaction. The first effect is often referred to as the Coulomb shift of the reaction energy. We investigate more specifically the second one, which is usually neglected. The relative importance of both effects is studied for ${\mathrm{\pi }}^{\pm }$-nucleus scattering at intermediate energies.

New differential cross section (dσ/dΩ), analyzing power (${\mathit{A}}_{\mathit{y}}$), and spin-rotation-depolarization (${\mathit{D}}_{\mathit{i}\mathit{j}}$) data for 500 MeV p→${+}^{12}$C${,}^{13}$C elastic scattering are reported. The dσ/dΩ and ${\mathit{A}}_{\mathit{y}}$ data span scattering angles from approximately 5°–37° c.m., while the ${\mathit{D}}_{\mathit{i}\mathit{j}}$ data cover 5°–26° c.m. Except at the largest angles, statistical errors are typically ±1% for dσ/dΩ, ±(0.01–0.02) for ${\mathit{A}}_{\mathit{y}}$, and ±(0.03–0.05) for the ${\mathit{D}}_{\mathit{i}\mathit{j}}$ observables. The data are compared to predictions of Dirac phenomenology and the relativistic-impulse-approximation–Dirac-equation model.

The systematics of quasifree scattering have been studied and parametrized for incident proton energies of 100–1000 MeV on a variety of targets. The observed position of the quasifree scattering peak at various emission angles closely tracks the kinematics for free nucleon-nucleon scattering. The peak widths are a function of the incident energy and of sinθ in the N-N center of mass. The angle-integrated cross section is described in terms of a peripheral interaction with a single nucleon in the target nucleus and has a threshold of 150–200 MeV. The angular variation of the cross section is either nearly isotropic or, at higher energies, exponential in cosθ. The simple parametrization derived here allows a semiquantitative estimate of quasifree scattering peaks with no adjustable parameters.

Differential cross sections were measured for 50 MeV ${\mathrm{\pi }}^{+}$ and ${\mathrm{\pi }}^{\mathrm{-}}$ elastic scattering from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and for 50 MeV ${\mathrm{\pi }}^{+}$ inelastic scattering to the (4.44 MeV, $2^{+}$), (7.65 MeV, $0_2^{+}$), (9.64 MeV, $3^{\mathrm{-}}$), (12.71 MeV, $1^{+}$), and (15.11 MeV, $1^{+}$) levels in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Comparisons of the data obtained in this study to data taken previously for these states resolve discrepancies between the earlier data sets. Using a recently discussed procedure, one-step and coupled-channels calculations using a modified MSU potential were performed. The results of both one-step and coupled-channels calculations describe the data for the ground, first, and third excited states, indicative of the collective isoscalar structure of those states. The one-step analysis fails to describe the excitation of the $0_2^{+}$ state. The coupled-channels calculations are more successful in describing those data, indicating that the failure of the one-step calculations may be attributed to coupled-channels effects.

The distortion behavior of the nucleon structure function in the nuclear medium is extensively studied by the constituent-quark model. The nuclear medium makes the oscillator constants of the three constituent quarks in a bound nucleon weaken so as to soften the distribution of the constituent quarks inside a nucleon. In addition, this distribution is smeared by the Fermi motion among the bound nucleons. The sea quark distribution is hardened by the gluon recombination mechanism. The Mueller-Qiu mechanism is improved by taking the coexistence of nuclear shadowing and antishadowing into account and this formulation follows the momentum sum rule for the parton-quark system. A free parameter is chosen on the basis of the quantum chromodynamic vacuum model. The theoretical predications for a series of nuclei with 4≤A≤200 within the kinetic region 0.001≤x≤0.9 are in fair agreement with the existing lepton-nucleus data in the full x region. Especially, the model predicts that two crossover points of the cross-section ratios ${\mathit{R}}_{\mathrm{\mu }}$(x) with the horizontal axis ${\mathit{R}}_{\mathrm{\mu }}$(x)=1 at low x move in the x direction as the mass number A increases.

We have calculated the photon spectrum for the reaction ${\mathit{K}}^{\mathrm{-}}$d→Λnγ in order to consider the feasibility of its use in a determination of the Λ-n singlet and triplet scattering lengths. We have used realistic deuteron wave functions obtained from the Bonn potential, a Λ-n scattering wave function parametrized in terms of a scattering length and effective range, and an effective interaction obtained from an earlier calculation of Kp→Λγ including momentum dependence through O(p/m). We find that the photon spectrum is sensitive to the choice of Λ-n scattering lengths, yet relatively insensitive to the choice of deuteron wave functions, to momentum dependence in the transition operator, and to the contributions from other intermediate channels involving ΣN→Λn conversions.

Pion-nucleon scattering is studied for pion laboratory momenta from 2 to 5 GeV/c using a relativistic optical model. ${\mathrm{\Pi }}^{\pm }$-p elastic differential, total elastic, and total cross sections and ${\mathrm{\pi }}^{\pm }$-p polarizations are calculated and compared with the experimental data.

The strangeness production in antiproton annihilation on nuclei is investigated by means of a cascade-type model, within the frame of the conventional picture of the annihilation on a single nucleon followed by subsequent rescattering proceeding in the hadronic phase. The following hadrons are introduced: N, Λ, Σ, Λ¯, π, η, ω, K, and K¯ and, as far as possible, the experimental reaction cross sections are used in our simulation. The numerical results are compared with experimental data up to 4 GeV/c. The Λ¯ yield is correctly reproduced, while the Λ and ${\mathit{K}}_{\mathit{s}}$ yields are overestimated in the p¯Ta and p¯Ne cases. On the other hand, the rapidity and perpendicular momentum distributions are well reproduced. It is shown that total strange yield is not very much affected by the associated production taking place during the rescattering process. It is also shown that the Λ/${\mathit{K}}_{\mathit{s}}$ ratio is largely due to the strangeness exchange reactions induced by antikaons. In particular, values of the order of 1 to 3 are expected in the energy range investigated here, independently of the detail of the hadronic phase dynamics. Finally, it is stressed that rapidity distributions are consistent with the rescattering process. Comparison with other works and implications of our results are examined.

The spectral shapes of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$ beta decays have been measured with a beta spectrograph specifically designed to examine the spectral effect of weak magnetism. Writing the weak magnetism correction to the beta spectra as (1+${\mathrm{\alpha }}_{\pm }$E) we find the difference ${\mathrm{\alpha }}_{\mathrm{-}}$-${\mathrm{\alpha }}_{+}$=(1.24±0.42)%/MeV, in agreement with the conserved vector current prediction.

Recent experiments observed unexpectedly strong interference between the E1-E1 and M1-M1 2γ decay modes of the $0^{+}$ (6.05 MeV) state in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. We present the results of a detailed calculation which evaluates the two-photon amplitude between realistic nonspurious many-body wave functions derived from a large basis SU(3) shell-model calculation, including up to 5ħω of excitation. It is found that, as a result of strong cancellation between contributions to the transition polarizability from the giant dipole states built on the closed shell and the deformed (6.05 MeV) $0^{+}$ state, the 2E1 matrix element is greatly suppressed. Since the standard one-body M1 operator cannot excite the closed shell, strong cancellations are not seen in this case. The resulting 2M1 decay mode becomes competitive with the 2E1 decay, although it is still underestimated by the calculations.

The E1 astrophysical S factor for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{16}$O reaction is studied using R-matrix theory. The constraints on this quantity from the α-particle spectrum following ${}_{}{}^{16}{}_{}{}^{}\mathrm{N}$ β decay are investigated with a set of pseudodata in an attempt to identify what additional information might be extracted from future measurements. The possibility of an experimental separation of the p- and f-wave α particles is discussed. Additional precise measurements of the β-delayed α particles at total center-of-mass energies near 1.0 MeV and the (α,γ) cross section at energies below and above previous measurements are particularly useful in constraining the S factor.

In exotic decay studies, the lifetime of alpha emission occurs crucially in the branching ratio calculation. In this work, we extend our previous exotic decay model to calculate the same. But, in this case unlike in the exotic decay, the redistribution of charge for given masses of the fragments has to be taken into account since the charge-to-mass ratio of the alpha fragment differs from that of the parent nucleus. We have therefore modified the Yukawa-plus-exponential potential in the post-scission region in our model suitably so as to allow the required charge redistribution among the fragments in the region between sharp contact and the point up to which the finite-range effects persist. The success of this model for alpha decay is as good as for the exotic decay studies.

A separable representation of the Paris interaction is used as input for the investigation of various nuclear matter properties. The faithfulness of the separable representation is checked by comparison with results previously obtained from the original Paris interaction. Calculations are performed for four different values of the Fermi momentum, namely ${\mathit{k}}_{\mathit{F}}$=1.10, 1.36, 1.55, and 1.75 ${\mathrm{fm}}^{\mathrm{-}1}$. One evaluates the contributions to the quasiparticle potential energy that are of first, second, and third order in the reaction matrix. The momentum distribution n(k) in the correlated ground state is calculated up to second order in the reaction matrix. For 0<k<2 ${\mathrm{fm}}^{\mathrm{-}1}$, it mainly depends upon the ratio k/${\mathit{k}}_{\mathit{F}}$; in the domain 2<k<4.5 ${\mathrm{fm}}^{\mathrm{-}1}$, it is accurately reproduced by the expression 1/7${\mathit{k}}_{\mathit{F}}^5$${\mathit{e}}^{\mathrm{-}1.6\mathit{k}}$, with k and ${\mathit{k}}_{\mathit{F}}$ in units of ${\mathrm{fm}}^{\mathrm{-}1}$. The quasiparticle strength at the Fermi surface is calculated, as well as the mean-square deviation of the one-body density matrix from that of the unperturbed Fermi sea: This quantity gives an estimate of the minimum value of the norm of the difference between the one-body density matrix of a correlated nucleus and that associated with any Slater determinant. The average kinetic energy per nucleon is evaluated. Various contributions to the average binding energy per nucleon are investigated in the framework of Brueckner’s expansion; particular attention is paid to the dependence of the calculated binding energy upon the choice of the ‘‘auxiliary’’ potential which is added to and subtracted from the Hamiltonian before performing the expansion. One also evaluates diagrams that are characteristic of the difference between the Green’s function and the Brueckner hole-line expansions. The fulfillment of the Hugenholtz–Van Hove theorem is studied.

A consistent analysis of E2 transition probabilities for nine neutron-deficient even-even Se, Kr, and Sr isotopes has been performed, based on previous parametrizations for these nuclei within the proton-neutron interacting-boson model, from which boson effective charges ${\mathit{e}}_{\mathrm{\pi }}$ and ${\mathit{e}}_{\nu }$ are deduced. Two sets of effective charges are obtained, one set having ${\mathit{e}}_{\mathrm{\pi }}$≊${\mathit{e}}_{\nu }$ for most of the nuclei studied, and the other set having ${\mathit{e}}_{\mathrm{\pi }}$ substantially larger than ${\mathit{e}}_{\nu }$ for most of the nuclei. For both sets, ${\mathit{e}}_{\mathrm{\pi }}$ tends to decrease with increasing neutron number, while ${\mathit{e}}_{\nu }$ is roughly constant. More information on mixed-symmetry states is needed to determine which set is valid.