Search

The study of the $^{17}\mathrm{O}(n,\ensuremath{\alpha})^{14}\mathrm{C}$ reaction has been performed by means of the Trojan horse method (THM) applied to the quasifree $^{2}\mathrm{H}(^{17}\mathrm{O},\ensuremath{\alpha}^{14}\mathrm{C})^{1}\mathrm{H}$ reaction induced at a beam energy of 43.5 MeV. The THM allowed us to study the 8121-keV $^{18}\mathrm{O}^{*}$ resonant level, for which the previous THM investigation pointed out the ability of the method to overcome the centrifugal barrier suppression effects in the entrance channel. Here, in view of the developments of the method for resonant reactions, the detailed analysis of the performed experiment will be discussed, focusing on the extraction of the 8121-keV resonance strength for which no information is present in scientific literature. Moreover, the experimental results clearly show the excitation of the subthreshold level centered at $\ensuremath{-}6$ keV in the center-of-mass system, which is fundamental to determine the $^{17}\mathrm{O}(n,\ensuremath{\alpha})^{14}\mathrm{C}$ reaction rate of astrophysical interest. Finally, a new recommended reaction rate is presented for future astrophysical application.

Proton radioactivity from 117 La was re-investigated with much improved statistics and precision. Only the ground-state proton decay ( E p = 813 ( 3 ) keV , T 1 / 2 = 20.1 ( 25 ) ms ) was observed, no evidence for a previously reported isomeric proton decay was found. Prompt γ rays in 117 La were identified using the Recoil–Decay Tagging method. Overall the data indicate that the proton-emitting state is associated with a K π = 3 / 2 + configuration, in agreement with all the published proton-decay calculations and predictions for the ground-state configuration of 117 La calculated in the framework of either adiabatic or non-adiabatic particle models. However, this is not in agreement with the most recent state-of-the-art quasi-particle non-adiabatic model calculations which predict a K π = 7 / 2 − configuration.

The clustering of $\ensuremath{\alpha}$ particles in atomic nuclei results in the self-organization of various geometrical arrangements at the femtometer scale. The one-dimensional alignment of multiple $\ensuremath{\alpha}$ particles is known as linear-chain structure, evidence of which has been highly elusive. We show via resonant elastic and inelastic $\ensuremath{\alpha}$ scattering of a radioactive $^{10}\mathrm{Be}$ beam that excited states in the neutron-rich nucleus $^{14}\mathrm{C}$ agree with recent predictions of linear-chain structure based on an antisymmetrized molecular dynamics model.

The $^{17}\text{O}(p,\ensuremath{\alpha})^{14}\text{N}$ and $^{17}\text{O}(p,\ensuremath{\gamma})^{18}\text{F}$ reactions are of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RGs), asymptotic giant branch (AGB) stars, massive stars, and classical novae. In particular, they govern the destruction of $^{17}\text{O}$ and the formation of the short-lived radioisotope $^{18}\text{F}$, which is of special interest for $\ensuremath{\gamma}$-ray astronomy. At temperatures typical of the above-mentioned astrophysical scenario, $T=0.01$--0.1 GK for RG, AGB, and massive stars and $T=0.1$--0.4 GK for a classical nova explosion, the $^{17}\text{O}(p,\ensuremath{\alpha})^{14}\text{N}$ reaction cross section is dominated by two resonances: one at about ${E}_{R}^{cm}=65$ keV above the $^{18}\text{F}$ proton threshold energy, corresponding to the ${E}_{X}=5.673$ MeV level in $^{18}\text{F}$, and another one at ${E}_{R}^{cm}=183$ keV $({E}_{X}=5.786$ MeV). We report on the indirect study of the $^{17}\text{O}(p,\ensuremath{\alpha})^{14}\text{N}$ reaction via the Trojan Horse method by applying the approach recently developed for extracting the strength of narrow resonance at ultralow energies. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature. This value was used as input parameter for reaction-rate determination and its comparison with the result of the direct measurement is also discussed in the light of the electron screening effect.

The proton decay of $^{53}\mathrm{Co}^{m}$($3174.1\phantom{\rule{4.pt}{0ex}}\text{keV},19/{2}^{\ensuremath{-}}$) was investigated via the fragmentation of a $^{58}\mathrm{Ni}$ primary beam. The proton-decay energy was determined with an improved precision to be $1558\phantom{\rule{0.16em}{0ex}}(8)\phantom{\rule{4.pt}{0ex}}\text{keV}$. With this new result and the mass of $^{53}\mathrm{Co}^{m}$, the $^{52}\mathrm{Fe}$ mass excess was derived to be $\ensuremath{-}48\phantom{\rule{0.16em}{0ex}}330\phantom{\rule{0.16em}{0ex}}(8)\phantom{\rule{4.pt}{0ex}}\text{keV}$, which is in good agreement with the AME12 value. A new recommended value of $\ensuremath{-}48\phantom{\rule{0.16em}{0ex}}331.6\phantom{\rule{0.16em}{0ex}}(49)\phantom{\rule{4.pt}{0ex}}\text{keV}$ is given.

The excitation function for the fusion–evaporation reaction Si 28 + Ni 64 has been measured down to a cross section of 25 nb. This is the first observation of fusion hindrance at extreme sub-barrier energies for a system with a small, negative Q-value ( − 1.78 MeV ). This result is further proof that heavy-ion fusion hindrance, reported earlier only for systems with large, negative Q-values, is a general phenomenon. The measured behavior can be reproduced by coupled-channels calculations with a modified ion–ion potential incorporating the effects of nuclear incompressibility.

The (8)B(alpha,p)(11)C reaction is part of the network that can bypass the triple a process leading to the production of (12)C. We have measured the astrophysical reaction rate for this reaction by studying the inverse (11)C(p,alpha)(8)B process. The radioactive (11)C beam was produced via the p((11)B,(11)C)n reaction using the in-flight facility at the ATLAS accelerator. The astrophysical reaction rate obtained from the excitation function measured in the energy range E(x)=8.8-10 MeV was found to be a factor of 10-50 higher than previous estimates.

We have measured the fusion cross sections of the 12C(13C, p)24Na reaction through off-line measurement of the beta-decay of 24Na using the beta-gamma coincidence method. Our new measurements in the energy range of Ec.m. = 2.6-3.0 MeV do not show an obvious S-factor maximum but a plateau. Comparison between this work and various models is presented., Comment: 3 pages, 3 figures, Talk at the "10th International Conference on Nucleus-Nucleus Collisions", Beijing, 16-21 August 2009

A multiple sampling ionization chamber (MUSIC) was developed for use in conjunction with the Atlas scattering chamber (ATSCAT). This chamber was developed to study the (α, p) reaction in stable and radioactive beams. The gas filled ionization chamber is used as a target and detector for both particles in the outgoing channel (p + beam particles for elastic scattering or p + residual nucleus for (α, p) reactions). The MUSIC detector is followed by a Si array to provide a trigger for anode events. The anode events are gated by a gating grid so that only (α, p) reactions where the proton reaches the Si detector result in an anode event. The MUSIC detector is a segmented ionization chamber. The active length of the chamber is 11.95 in. and is divided into 16 equal anode segments (3.5 in. × 0.70 in. with 0.3 in. spacing between pads). The dead area of the chamber was reduced by the addition of a Delrin snout that extends 0.875 in. into the chamber from the front face, to which a mylar window is affixed. 0.5 in. above the anode is a Frisch grid that is held at ground potential. 0.5 in. above the Frisch grid is a gating grid. The gating grid functions as a drift electron barrier, effectively halting the gathering of signals. Setting two sets of alternating wires at differing potentials creates a lateral electric field which traps the drift electrons, stopping the collection of anode signals. The chamber also has a reinforced mylar exit window separating the Si array from the target gas. This allows protons from the (α, p) reaction to be detected. The detection of these protons opens the gating grid to allow the drift electrons released from the ionizing gas during the (α, p) reaction to reach the anode segment below the reaction.

Cross section measurements of the reactions ${}^{90,92}$Zr($p$,$\ensuremath{\gamma}$)${}^{91,93}$Nb were performed using the National Superconducting Cyclotron Laboratory Summing NaI(Tl) detector at the University of Notre Dame. These reactions are part of the nuclear reaction flow for the synthesis of the light $p$ nuclei. For the ${}^{90}$Zr($p$,$\ensuremath{\gamma}$)${}^{91}$Nb reaction the new measurement resolves the disagreement between previous results. For the ${}^{92}$Zr($p$,$\ensuremath{\gamma}$)${}^{93}$Nb reaction the present work reports the first measurement of this reaction cross section. Both reaction cross sections are compared to theoretical calculations and a very good agreement with the standard non-smoker model is observed.

In an effort to investigate the production of ${}^{74}$Se in $p$-process nucleosynthesis, the ${}^{74}$Ge($p$,$\ensuremath{\gamma}$)${}^{75}$As reaction cross section was measured in the relevant energy range of ${E}_{p}=1.6$--4.2 MeV. The measurements were carried out using the NSCL SuN detector at the University of Notre Dame. The results are in good agreement with previous work, extending the measurements to both lower and higher energies. The measurements are compared to theoretical predictions using the non-smoker and talys nuclear reaction codes. New and improved reaction rates are offered, and these reaction rates are used in a 25M${}_{\ensuremath{\bigodot}}$ Type II Supernova model to study their impact on the production of ${}^{74}$Se.

The fusion excitation function of 60 Ni + 100 Mo has been measured from above the Coulomb barrier down to a cross section around 2 μb, looking for coupling and hindrance effects in this soft medium-mass system with positive Q-values for several neutron transfer channels. A comparison is made with previous results for 64 Ni + 100 Mo where no Q > 0 transfer channels exist and the hindrance effect is quite clear. The two excitation functions are very similar, as well as the corresponding logarithmic derivatives showing analogous saturations below the barrier. It appears that transfer couplings to Q > 0 channels seem to play a marginal role near and below the barrier for 60 Ni + 100 Mo , even if measurements of cross sections lower than 1 μb would be needed also for this system. Coupled-channels calculations confirm these observations and indicate that multi-phonon excitations dominate the fusion dynamics in the whole measured energy range.

The fusion excitation function of ${}^{32}$S + ${}^{48}$Ca has been experimentally studied in a wide energy range, from above the Coulomb barrier down to cross sections in the sub-$\ensuremath{\mu}$b region. The measurements were done at INFN--Laboratori Nazionali di Legnaro, using the ${}^{32}$S beam from the XTU Tandem accelerator. The excitation function has a smooth behavior below the barrier, and no evident hindrance character shows up in the measured energy region. The fusion barrier distribution has a peculiar shape with two distinct peaks of similar height, lower and higher than the Aky\"uz-Winther barrier. Coupled-channels calculations using the M3Y + repulsion potential are presented for this system and for ${}^{36}$S + ${}^{48}$Ca. The results of these calculations give a good account of the data, and indicate the influence of one- and two-nucleon transfer channels with positive $Q$ values, which are only open for ${}^{32}$S + ${}^{48}$Ca.

The fusion excitation function of 32S + 48Ca has been experimentally studied in a wide energy range, from above the Coulomb barrier down to cross sections in the sub- b region. The measurements were done at INFN-Laboratori Nazionali di Legnaro, using the 32S beam from the XTU Tandem accelerator. The excitation function has a smooth behavior below the barrier with a rather flat slope, and no maximum of astrophysical factor S vs. energy has been observed. However, other interesting features of the dynamics of this system can be noted. In particular, the fusion barrier distribution has an unusual shape with two peaks of similar height, lower and higher than the Akyuz-Winther barrier. Preliminary coupled- channels calculations and a comparison with nearby systems have been performed to get information on the possible influence of nucleon transfer channels with positive Q-value.

The fusion excitation function of ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ has been measured from well above the Coulomb barrier, down to low energies where the cross section is as small as $\ensuremath{\simeq}$20 $\ensuremath{\mu}$b, and the astrophysical $S$ factor possibly reaches a maximum vs energy. The results of coupled-channels calculations using the $\mathrm{M}3\mathrm{Y}+\mathrm{repulsion}$ potential are presented. A detailed comparison is made with recently published data on the fusion of ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$ and of ${}^{48}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, including the excitation functions, their low-energy slopes and the barrier distributions. The presence of the fusion hindrance phenomenon in all cases is pointed out, as well as the influence of the strong octupole excitation in ${}^{40}$Ca and of nucleon transfer channels with positive $Q$ values in ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$.

The fusion excitation function of 32S+48Ca has been measured in a wide energy range, from above the Coulomb barrier down to cross sections in the sub-μb region. The excitation function has a smooth behavior below the barrier with a rather flat slope, and no maximum of astrophysical factor S vs. energy has been observed. However, other interesting features of the dynamics of this system can be noted. In particular, the fusion barrier distribution has an unusual shape with two peaks of similar height, lower and higher than the Akyuz-Winther barrier. Preliminary coupledchannels calculations and a comparison with nearby systems yield information on the possible influence of nucleon transfer channels with positive Q-value.

The fusion cross section of 60 Ni + 100 Mo has been measured down to microbarn level, looking for hindrance at low energy, in a system with positive Q-values for neutron transfer. The measured cross sections look similar to those of the nearby 64 Ni + 100 Mo, but no conclusive statement can be made at this stage, as to the onset of hindrance in this system.

Fusion data for $^{13}$C+$^{13}$C, $^{12}$C+$^{13}$C and $^{12}$C+$^{12}$C are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. The fusion is determined by ingoing-wave-boundary conditions (IWBC) that are imposed at the minimum of the pocket in the entrance channel potential. Quadrupole and octupole transitions to low-lying states in projectile and target are included in the calculations, as well as mutual excitations of these states. The effect of one-neutron transfer is also considered but the effect is small in the measured energy regime. It is shown that mutual excitations to high-lying states play a very important role in developing a comprehensive and consistent description of the measurements. Thus the shapes of the calculated cross sections for $^{12}$C+$^{13}$C and $^{13}$C+$^{13}$C are in good agreement with the data. The fusion cross sections for $^{12}$C+$^{12}$C determined by the IWBC are generally larger than the measured cross sections but they are consistent with the maxima of some of the observed peak cross sections. They are therefore expected to provide an upper limit for the extrapolation into the low-energy regime of interest to astrophysics., Comment: 34 pages, 17 figures

A measurement of the $\ensuremath{\beta}$-delayed $\ensuremath{\alpha}$ decay of $^{16}\mathrm{N}$ using a set of twin ionization chambers is described. Sources were made by implantation, using a $^{16}\mathrm{N}$ beam produced via the In-Flight Technique. The energies and emission angles of the $^{12}\mathrm{C}$ and $\ensuremath{\alpha}$ particles were measured in coincidence and very clean $\ensuremath{\alpha}$ spectra, down to energies of $450$ keV, were obtained. The structure of the spectra from this experiment is in good agreement with results from previous measurements. An analysis of our data with the same input parameters as used in earlier studies gives ${S}_{E1}(300)=86\ifmmode\pm\else\textpm\fi{}22$ keVb for the $E1$ component of the $S$-factor. This value is in excellent agreement with results obtained from various direct and indirect measurements. In addition, the influence of new measurements including the phase shift data from Tischhauser et al. on the value of ${S}_{E1}(300)$ is discussed.

Fusion evaporation cross sections for the {sup 27}Al+{sup 45}Sc (Q=9.63 MeV) system are measured down to about 300 nb. Deviations from standard coupled-channels calculations were observed in this system at the lowest energies. The steep fall-off of the fusion cross sections can be reproduced by calculations using a shallow potential model, which was originally developed to explain the hindrance behavior of heavy-ion fusion in medium-mass systems with negative Q values. Comparisons of the hindrance behavior between the present experiment and other systems, for example, {sup 28}Si+{sup 30}Si (Q=14.3 MeV) and {sup 36}S+{sup 48}Ca (Q=7.55 MeV) are presented.

We have studied the neutron-transfer reactions {sup 11,12}B(d,p){sup 12,13}B in inverse kinematics to obtain information about the neutron-capture reactions {sup 11,12}B(n,{gamma}). These capture reactions are suggested to play a role in seeding r-process nucleosynthesis through the production of light, neutron-rich nuclei. The neutron spectroscopic factors of the states in {sup 12,13}B were deduced and the branching ratio of the neutron-unbound state at E{sub X}=3.389 MeV in {sup 12}B was obtained to provide the ratio of partial widths, {Gamma}{sub n}/{Gamma}{sub {gamma}}. The reaction rates for {sup 11,12}B(n,{gamma}) are estimated for direct captures and resonant captures and compared with previous compilations. The astrophysical implications, especially for neutrino-driven wind models in core-collapse supernovae, are discussed in the r-process network framework using our updated reaction rates.

The measurement of the excitation function for fusion evaporation reactions in the system $^{40}\mathrm{Ca}+^{48}\mathrm{Ca}$ ($Q=$ 4.56 MeV) has been extended downward by two orders of magnitude with respect to previous cross section data. A first indication of an $S$-factor maximum in a system with a positive $Q$ value has been observed. In addition a correlation between fusion hindrance and neutron excess $N\ensuremath{-}Z$ has been found for the Ca $+$ Ca, Ni $+$ Ni, and Ca $+$ Zr systems.

We report on a study of the structure of the unbound nucleus {sup 7}He utilizing the proton-removal reaction {sup 2}H({sup 8}Li,{sup 3}He){sup 7}He. Combining the present results with those of our prior measurements of the neutron-adding reaction {sup 2}H({sup 6}He,p){sup 7}He, a consistent picture emerges for the low-lying excitations in {sup 7}He. Specifically, the negative-parity sequence of resonances, in order of excitation energies, is consistent with 3/2{sup -},1/2{sup -}, and 5/2{sup -}. The stable-beam reactions {sup 2}H({sup 7}Li,t){sup 6}Li and {sup 2}H({sup 7}Li,{sup 3}He){sup 6}He were also measured. The results are compared with the predictions of nuclear structure models, including those of ab initio quantum Monte Carlo calculations.

The capture cross sections and fission fragment angular distributions were measured for the reaction of $^{50}\mathrm{Ti}$ with $^{208}\mathrm{Pb}$ at center of mass projectile energies (${E}_{\mathrm{c}.\mathrm{m}.}$) of 183.7, 186.2, 190.2, 194.2, and 202.3 MeV (${E}^{*}=14.2$, 16.6, 20.6, 24.7, and 32.7 MeV). From fitting the backward angle fragment angular distributions, the cross sections for quasifission and fusion-fission and ${P}_{\mathrm{CN}}$, the probability that the colliding nuclei go from the contact configuration to inside the fission saddle point, were deduced. These quantities, along with the known values of the evaporation residue production cross sections for this reaction, were used to deduce values of the survival probabilities, ${W}_{\mathrm{sur}}$, for this reaction as a function of excitation energy. The deduced values of ${P}_{\mathrm{CN}}$ and ${W}_{\mathrm{sur}}$ and their dependence on excitation energy differ from some current theoretical predictions of these quantities.

Precision measurements were carried out to test the similarities between the ground states of $^{76}\mathrm{Ge}$ and $^{76}\mathrm{Se}$. The extent to which these two nuclei can be characterized as consisting of correlated pairs of neutrons in a BCS-like ground state was studied. The pair removal $(p,t)$ reaction was measured at the far forward angle of ${3}^{\ifmmode^\circ\else\textdegree\fi{}}$. The relative cross sections are consistent (at the 5% level) with the description of these nuclei in terms of a correlated pairing state outside the $N=28$ closed shells with no pairing vibrations. Data were also obtained for $^{74}\mathrm{Ge}$ and $^{78}\mathrm{Se}$.

Single‐neutron transfer with the (d,p) reaction in inverse kinematics has been used to study the properties of the light nuclei 9Li and 7He. The results for 9Li and 7Heg.s. are compared to the predictions of ab‐initio models of nuclear structure. Different possibilities for excited states in 7He are discussed in the context of other recent experimental studies of 7He.

There are many new results in the study of the heavy‐ion fusion hindrance phenomenon at extreme sub‐barrier energies since Fusion03. Some of them have been published. Presented are some new results, including the first evidence in fusion hindrance for a system with small negative Q‐value, 28Si + 64Ni, and the impact of fusion hindrance on reactions of interest to astrophysics.

The excitation function for the fusion-evaporation reaction 64Ni+100Mo has been measured down to a cross-section of ~5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep fall-off of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at E_s=120.6 MeV, which corresponds to 90% of the reference energy E_s^ref, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass A=100-200 is presented in order to explore a possible dependence of the fusion hindrance on nuclear structure., 10 pages, 9 figures, Submitted to Phys. Rev. C

We have studied the properties of low‐lying levels in 7He using the d(6He,p)7He reaction. Recent measurements of 8He breakup and the p(8He,d)7He reaction present conflicting results on 7He first excited state A broad resonance observed in the present work at EX = 2.2−0.1+0.2 MeV is identified with the expected 1/2− spin‐orbit partner to the 7He ground state. No evidence is seen of a lower first‐excited state that was recently reported.

The direct capture contribution for 13N(p,γ)14O has been determined more precisely with the peripheral transfer reaction, 14N(13N,14O)13C at the energy of 11.8 MeV/nucleon using the ANC technique. The updated 13N(p,γ)14O reaction rate is about 2.5 times larger than the standard REACLIB rate in the temperature range 0.1 < T9 < 0.3. The transition condition from the cold to hot CNO cycles has been determined with this updated rate. The influences incurred by this update have been investigated with two one‐zone nova models.

We have performed precision laser spectroscopy on individual $^{6}\mathrm{H}\mathrm{e}$ (${t}_{1/2}=0.8\text{ }\text{ }\mathrm{s}$) atoms confined and cooled in a magneto-optical trap, and measured the isotope shift between $^{6}\mathrm{H}\mathrm{e}$ and $^{4}\mathrm{H}\mathrm{e}$ to be $43\text{ }\text{ }194.772\ifmmode\pm\else\textpm\fi{}0.056\text{ }\text{ }\mathrm{M}\mathrm{H}\mathrm{z}$ for the ${2}^{3}{S}_{1}\ensuremath{-}{3}^{3}{P}_{2}$ transition. Based on this measurement and atomic theory, the nuclear charge radius of $^{6}\mathrm{H}\mathrm{e}$ is determined for the first time in a method independent of nuclear models to be $2.054\ifmmode\pm\else\textpm\fi{}0.014\text{ }\text{ }\mathrm{f}\mathrm{m}$. The result is compared with the values predicted by a number of nuclear structure calculations and tests their ability to characterize this loosely bound halo nucleus.

$^{13}\mathrm{N}(p,\ensuremath{\gamma})^{14}\mathrm{O}$ is one of the key reactions which trigger the onset of the hot CNO cycle. This transition occurs when the proton capture rate on $^{13}\mathrm{N}$ is faster, due to increasing stellar temperature $(\ensuremath{\geqslant}{10}^{8}\phantom{\rule{0.3em}{0ex}}\mathrm{K})$, than the $^{13}\mathrm{N}$ $\ensuremath{\beta}$-decay rate. The rate of this reaction is dominated by the resonant capture through the first excited state of $^{14}\mathrm{O}$ $({E}_{r}=0.528\phantom{\rule{0.3em}{0ex}}\text{MeV})$. However, through constructive interference, direct capture below the resonance makes a non-negligible contribution to the reaction rate. We have determined this direct contribution by measuring the asymptotic normalization coefficient for $^{14}\mathrm{O}\ensuremath{\rightarrow}^{13}\mathrm{N}+p$. In our experiment, an $11.8\phantom{\rule{0.3em}{0ex}}\text{MeV}∕\text{nucleon}$ $^{13}\mathrm{N}$ radioactive beam was used to study the $^{14}\mathrm{N}(^{13}\mathrm{N},^{14}\mathrm{O})^{13}\mathrm{C}$ peripheral transfer reaction, and the asymptotic normalization coefficient, ${({C}_{{p}_{1∕2}}^{^{14}\mathrm{O}})}^{2}=29.0\ifmmode\pm\else\textpm\fi{}4.3\phantom{\rule{0.3em}{0ex}}{\text{fm}}^{\ensuremath{-}1}$, was extracted from the measured cross section. The radiative capture cross section was estimated using an $R$-matrix approach with the measured asymptotic normalization coefficient and the latest resonance parameters. We find the $S$ factor for $^{13}\mathrm{N}(p,\ensuremath{\gamma})^{14}\mathrm{O}$ to be larger than previous estimates. Consequently, the transition from the cold to hot CNO cycle for novae would be controlled by the slowest proton capture reaction $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$.

Fusion-evaporation reactions induced by $110\phantom{\rule{0.3em}{0ex}}\text{MeV}$ $^{11}\mathrm{B}$ and radioactive $^{11}\mathrm{C}$ on $^{87}\mathrm{Rb}$ targets have been studied by measuring evaporation residue--light particle coincidences. The proton to $\ensuremath{\alpha}$ particle ratio in each reaction has been derived and compared with predictions from statistical model calculations. These calculations account rather well for the experimental data, when a small empirical adjustment of the emission barrier is performed, in agreement with earlier results. No evidence is found for predicted temperature and isospin modification of the binding energies. The possibility of a further study of isospin and temperature dependent effects in fusion-evaporation reactions with radioactive beams is discussed.

The reaction 17 O (n , α )14 C was studied using virtual neutrons coming from the quasi-free deuteron break-up in the three body reaction 17 O +d → α +14 C +p . This technique, called virtual neutron method, extends the Trojan Horse method to neutron-induced reactions allowing to study the reaction cross section avoiding the suppression effects coming from the penetrability of the centrifugal barrier. For incident neutron energies from thermal up to a few hundred keV, direct experiments have shown the population of two out of three expected excited states at energies 8213 keV and 8282 keV and the influence of the sub-threshold level at 8038 keV. In the present experiment the 18 O excited state at E * = 8.125 MeV, missing in the direct measurement, is observed. The angular distributions of the populated resonances have been measured for the first time. The results unambiguously indicate the ability of the method to overcome the centrifugal barrier suppression effect and to pick out the contribution of the bare nuclear interaction.

Carbon burning is a crucial process for a number of important astrophysical scenarios. The lowest measured energy is around E$_{\rm c.m.}$=2.1 MeV, only partially overlapping with the energy range of astrophysical interest. The currently adopted reaction rates are based on an extrapolation which is highly uncertain because of potential resonances existing in the unmeasured energy range and the complication of the effective nuclear potential. By comparing the cross sections of the three carbon isotope fusion reactions, ${}^{12}$C+${}^{12}$C, ${}^{12}$C+${}^{13}$C and ${}^{13}$C+${}^{13}$C, we have established an upper limit on the molecular resonance strengths in ${}^{12}$C+${}^{12}$C fusion reaction. The preliminary results are presented and the impact on nuclear astrophysics is discussed., Comment: 4 pages, 3 figures, FUSION11 conference proceeding