One-nucleon transfer reactions to discrete levels induced by a 793 MeV 16O beam on a 208Pb target

One-proton and one-neutron stripping reactions induced by a 793 MeV ¹⁶O beam bombarding a ²⁰⁸Pb target have been studied at the GANIL facility using a high resolution energy-loss magnetic spectrometer. The reactions are governed by two semi-classical selection rules which are naturally contained in the one-step EFR-DWBA formalism. Relative intensities of the populated states are well reproduced by this formalism which, on the other hand, fails to correctly predict absolute cross section values.     

One-nucleon stripping reactions to discrete levels induced by a 793 MeV16O beam on a208Pb target

One-proton and one-neutron stripping reactions induced by a 793 MeV¹⁶O beam bombarding a²⁰⁸Pb target have been studied at the GANIL facility using a high resolution energy loss magnetic spectrometer. The reactions are governed by two semi classical selection rules which are naturally contained in the one-step EFR-DWBA formalism. Relative intensities of the populated states are well reproduced by this formalism which, on the other hand, fails to predict correctly absolute cross section values.     

Resonant photon scattering on the semi-magic nucleus 89Y up to 7 MeV

The semi-magic nucleus ⁸⁹Y has been investigated in a (γ,γ′) experiment at an endpoint energy of the bremsstrahlung of E₀ = 7 MeV. The scattered photons have been detected with a EUROBALL Cluster detector. The observed excitations are discussed in the framework of the shell model and a coupling of the unpaired proton to multi-phonon structures in the doubly even neighbours. Transitions above 4.7 MeV are considered to have E1 character. Around 6.3 MeV an unusually large concentration of E1 strength is found. Its origin is likely to correspond to similar structures in the ⁸⁸Sr and ⁹⁰Zr isotones which can be interpreted to result from the constructive interference of strong two-phonon amplitudes with weak admixtures from the low-energy tail of the giant dipole resonance.     

Direct surface-transfer reaction to the continuum states induced by a 1760 MeV 40Ar beam on 27Al and natTi target nuclei

The inclusive energy spectra of few-nucleon transfer reactions obtained by bombarding ²⁷Al and ^natTi target nuclei with the GANIL 1760 MeV ⁴⁰Ar beam have been analysed in terms of direct surface-transfer reactions populating the continuum states. The shape at forward angles of the various energy spectra and the corresponding angular distributions are well reproduced by a diffractional model calculation based on mutual excitation of the two residual partners. It turns out that one of the essential ingredients of the calculations is the Williams partial level density either of the target or of the projectile constructed only with the transferred nucleons or residual holes coupled to the ground state.     

A study of the reaction19F(α, n)22Na in the bombarding energy range 2·6 to 5·1 MeV

The total (α, n) reaction cross section for¹⁹F has been measured as a function of alpha energy in the energy range 2·6 to 5·1 MeV with a thin target. The excitation function exhibits a large number of resonances. The prominent amongst these for which theJ ^π values are known have been analysed to extract the partial widthsΓ ^α and Γ _n . Statistical analysis of the data in terms of strength function and average level spacing distribution has also been performed.     

The transfer reactions induced by 38 MeV 19F ions on 27Al

The reactions induced by 38 MeV ¹⁹F on ²⁷Al have been studied using the Tandem Van de Graaff accelerator at Harwell together with a mass identification system based on a combination of a Buechner magnetic spectrograph and position sensitive silicon detectors in the focal plane of the magnet. Comparison of the elastic scattering measurements with Coulomb cross sections provided an absolute normalisation to the measured reaction yields. Transfer reactions were measured as a function of emitted particle energy and angle for single nucleon pick-up and stripping and for 2, 3 and 4 particle stripping. Essential features of the experimental technique are outlined and the experimental results are presented. The significance of the energy spectra and angular distributions are discussed. The results of DWBA analyses of one-nucleon transfer reactions yield spectroscopic factors for levels in ²⁸Si, ²⁸Al and ²⁶Al which are in fair agreement with those obtained in other studies.     

Kinetics of carbon nanopillar formation on a pyrolytic graphite surface during reactions induced by a focused electron beam

The results from a series of height measurements of carbon nanopillars formed during residual hydrocarbon deposition on a pyrographite surface by a focused electron beam in an SEM are presented. The high initial velocity of the pillars’ vertical growth can be explained by the dominant role of surface diffusion in the influx of molecules to the irradiated area. It is shown that progressive contamination of the substrate at distances up to several micrometers from the point of impact of the primary beam delays growth, and, in the case of long-time exposure, results in the evaporation of the pillars.     

Peripheral Ar induced reactions at 44 MeV/u — similarities and deviations with respect to a high energy fragmentation process

Peripheral Ar reactions induced at GANIL at 44 MeV/u have been analyzed in the framework of the high energy fragmentation model. Several deviations from this model have been interpreted as due to the persistence of some collective effects at this intermediate energy.     

High beam quality by SBS phase conjugation of a single rod Nd-amplifier up to 140 W average output power

For pumping XUV plasma light sources with solid-state lasers and also for micromaterial processing, high beam quality and output power as well as simplicity of the pump lasers are crucial. The beam quality of high-power solid-state lasers can be significantly improved using phase-conjugating mirrors based on stimulated Brillouin scattering (SBS). Hence, SBS phase conjugation may prove one of the key technologies in this field. We describe a single-rod neodymium amplifier with 140 W average output power and nearly diffraction-limited beam. Because of automatic compensation of the thermal lensing by SBS phase conjugation, the output power can be tuned without changing the beam profile.     

A new cross-section measurement of reactions induced by <Superscript>3</Superscript>He particles on a carbon target

The production of intense beams of light radioactive nuclei can be achieved at the SPIRAL2 facility using intense stable beams accelerated by the driver accelerator and impinging on light targets. The isotope ¹⁴O is identified to be of high interest for future experiments. The excitation function of the production reaction ¹²C(³He, n)¹⁴O was measured between 7 and 35MeV. Results are compared with literature data. As an additional result, we report the first cross-section measurement for the ¹²C(³He,a alpha + n)¹⁰C reaction. Based on this new result, the potential in-target ¹⁴O yield at SPIRAL2 was estimated: 2.4×10¹¹ pps, for 1mA of ³He at 35MeV. This is a factor 140 higher than the in-target yield at SPIRAL1.     

Resonant phase conjugation as a saturated absorption process induced by a spatially modulated pump beam. application to strong-field lineshape studies

One shows that phase conjugation (PC) by degenerate four-wave mixing in resonant gas media can be interpreted as a saturated absorption (SA) process produced by a spatially-modulated pump beam. This allows us to directly link PC and SA lineshapes, and provides a general way for predicting PC linshapes. Some applications to the strong-field regime in two- and three-level systems are discussed.     

Enhancement of two-proton transfer in N = 82 nuclei: A study of 1p, 2p and (2p+2n) transfer reactions induced by 16O on 140Ce, 142Nd and 144Sm near the Coulomb barrier

One-proton, two-proton, and α-particle transfer have been studied on nuclei with closed neutron shell N = 82 using ¹⁶O beams of 63 to 66.5 MeV incident energy. Transfer probabilities defined in a semiclassical model are derived for the different reaction channels. For this purpose the Q-value and angular dependence of the cross section are discussed. The two-proton transfer to the ground states shows an enhancement by a factor 20–25 compared to other nuclei, showing the effect of the proton pairing in these nuclei (they correspond to equivalent neutron configurations in ^{108, 110, 112}Sn). The total transfer probability follows a common trend for all three target nuclei as a function of energy above the Coulomb barrier for the proton and two-proton transfer, respectively, but not for the four-nucleon transfer.     

Studying the ejection of light charged particles induced by 50 MeV <Superscript>3</Superscript>He ions upon interacting with a <Superscript>112</Superscript>Sn nucleus

Experimental double-differential and integral spectra of (³He, xp), (³He, xd), (³He, xt), (³He, x³He) and (³He, xα) reactions on ¹¹²Sn nuclei induced by 50 MeV 3He ions are presented. Theoretical calculations of the experimental inclusive spectra of the reactions are performed using the exciton model of preequilibrium decay. The corresponding mechanisms of reactions are determined. The experimental results can be used to develop new approaches in the theory of nuclear reactions, and to design safe and wasteless hybrid nuclear power plants.     

Acceleration of heavy multicharged ions up to 1 MeV from a cleaned solid target irradiated by a femtosecond laser pulse with an intensity of 10<Superscript>16</Superscript> W/cm<Superscript>2</Superscript>

A noticeable increase in the charge and energy of ions accelerated from a solid tungsten target irradiated by a femtosecond laser pulse with an intensity higher than 10¹⁶W/cm² has been found when the target surface is precleaned by a nanosecond laser pulse with an energy density of 3 J/cm². Tungsten ions with charges up to +29 and energies up to 1 MeV were detected in this case, while the charge and energy of tungsten ions from a target with an uncleaned surface do not exceed +3 and 12 keV, respectively.