779 research outputs found
The solvation and dissociation of 4-benzylaniline hydrochloride in chlorobenzene
A reaction scheme is proposed to account for the liberation of 4-benzylaniline from 4-benzylaniline hydrochloride, using chlorobenzene as a solvent at a temperature of 373 K. Two operational regimes are explored: âclosedâ reaction conditions correspond to the retention of evolved hydrogen chloride gas within the reaction medium, whereas an âopenâ system permits gaseous hydrogen chloride to be released from the reaction medium. The solution phase chemistry is analyzed by 1H NMR spectroscopy. Complete liberation of solvated 4-benzylaniline from solid 4-benzylaniline hydrochloride is possible under âopenâ conditions, with the entropically favored conversion of solvated hydrogen chloride to the gaseous phase thought to be the thermodynamic driver that effectively controls a series of interconnecting equilibria. A kinetic model is proposed to account for the observations of the open system
Single-neutron transfer from 11Be gs via the (p,d) reaction with a radioactive beam
The 11Be(p,d)10Be reaction has been performed in inverse kinematics with a
radioactive 11Be beam of E/A = 35.3 MeV. Angular distributions for the 0+
ground state, the 2+, 3.37 MeV state and the multiplet of states around 6 MeV
in 10Be were measured at angles up to 16 deg CM by detecting the 10Be in a
dispersion-matched spectrometer and the coincident deuterons in a silicon
array. Distorted wave and coupled-channels calculations have been performed to
investigate the amount of 2+ core excitation in 11Be gs. The use of "realistic"
11Be wave functions is emphasised and bound state form factors have been
obtained by solving the particle-vibration coupling equations. This calculation
gives a dominant 2s component in the 11Be gs wave function with a 16% [2+ x 1d]
core excitation admixture. Cross sections calculated with these form factors
are in good agreement with the present data. The Separation Energy prescription
for the bound state wave function also gives satisfactory fits to the data, but
leads to a significantly larger [2 x 1d] component in 11Be gs.Comment: 39 pages, 12 figures. Accepted for publication in Nuclear Physics A.
Added minor corrections made in proof to pages 26 and 3
Electromagnetic processes in strong crystalline fields
As an addendum to the NA63 proposal cite{Ande05}, we propose to measure 1) the Landau-Pomeranchuk-Migdal (LPM) effect in low- targets, 2) Magnetic suppression of incoherent bremsstrahlung resulting from exposure to an external field during the emission event, and 3) the bremsstrahlung emission from relativistic (), fully stripped Pb nuclei penetrating various amorphous targets. Concerning the LPM effect, both the 'traditional' Migdal approach and the modern treatment by Baier and Katkov display inaccuracies, i.e. a possible lack of applicability in low- targets. Moreover, the LPM effect has been shown to have a significant impact on giant air showers for energies in the EeV range - evidently processes in a low- material. A measurement of magnetic suppression is demanding in terms of necessary accuracy (an expected 15% effect), but would prove the existence of a basic interplay between coherent and incoherent processes, also believed to be significant in beamstrahlung emission. For bremsstrahlung from Pb: In contrast to earlier expectations, recent investigations have shown that the bremsstrahlung emission from heavy, relativistic particles does not appear with constant power for all photon energies up to the end-point given by the energy of the incident ion, but instead the spectrum has a peaked shape, due to the finite size of the nucleus. Beyond an energy of about , wher e corresponds to the energy transfer above which the protons in the nucleus can be considered quasi-free, the power-spectrum falls off quite steeply, eventually leaving pair production as the dominant energy loss mechanism for sufficiently high values of the Lorentz-factor
Search for {\eta}'(958)-nucleus bound states by (p,d) reaction at GSI and FAIR
The mass of the {\eta}' meson is theoretically expected to be reduced at
finite density, which indicates the existence of {\eta}'-nucleus bound states.
To investigate these states, we perform missing-mass spectroscopy for the (p,
d) reaction near the {\eta}' production threshold. The overview of the
experimental situation is given and the current status is discussed.Comment: 6 pages, 3 figures; talk at II Symposium on applied nuclear physics
and innovative technologies, September 24th - 27th, 2014, Jagiellonian
University, Krak\'ow Poland; to appear in Acta Physica Polonica
Core excitation in Coulomb breakup reactions
Within the pure Coulomb breakup mechanism, we investigate the one-neutron
removal reaction of the type A(a,b)X with Be and C
projectiles on a heavy target nucleus Pb at the beam energy of 60
MeV/nucleon. Our intention is to examine the prospective of using these
reactions to study the structure of neutron rich nuclei. Integrated partial
cross sections and momentum distributions for the ground as well as excited
bound states of core nuclei are calculated within the finite range distorted
wave Born approximation as well as within the adiabatic model of the Coulomb
breakup. Our results are compared with those obtained in the studies of the
reactions on a light target where the breakup proceeds via the pure nuclear
mechanism. We find that the transitions to excited states of the core are quite
weak in the Coulomb dominated process as compared to the pure nuclear breakup.Comment: Revtex format, five postscript figures included, to appear in Phys.
Rev.
Spectroscopy of -nucleus bound states at GSI and FAIR --- very preliminary results and future prospects ---
The possible existence of \eta'-nucleus bound states has been put forward
through theoretical and experimental studies. It is strongly related to the
\eta' mass at finite density, which is expected to be reduced because of the
interplay between the anomaly and partial restoration of chiral
symmetry. The investigation of the C(p,d) reaction at GSI and FAIR, as well as
an overview of the experimental program at GSI and future plans at FAIR are
discussed.Comment: 7 pages, 3 figures; talk at the International Conference on Exotic
Atoms and Related Topics (EXA2014), Vienna, Austria, 15-19 September 2014. in
Hyperfine Interactions (2015
\b{eta}-delayed three-proton decay of 31Ar
The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880
MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a
gaseous time projection chamber with optical readout allowing to record decay
events with emission of protons. In addition to \b{eta}-delayed emission of one
and two protons we have clearly observed the beta-delayed three-proton branch.
The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.
One-neutron removal reactions on light neutron-rich nuclei
A study of high energy (43--68 MeV/nucleon) one-neutron removal reactions on
a range of neutron-rich psd-shell nuclei (Z = 5--9, A = 12--25) has been
undertaken. The inclusive longitudinal and transverse momentum distributions
for the core fragments, together with the cross sections have been measured for
breakup on a carbon target. Momentum distributions for reactions on tantalum
were also measured for a subset of nuclei. An extended version of the Glauber
model incorporating second order noneikonal corrections to the JLM
parametrisation of the optical potential has been used to describe the nuclear
breakup, whilst the Coulomb dissociation is treated within first order
perturbation theory. The projectile structure has been taken into account via
shell model calculations employing the psd-interaction of Warburton and Brown.
Both the longitudinal and transverse momentum distributions, together with the
integrated cross sections were well reproduced by these calculations and
spin-parity assignments are thus proposed for B, C, N,
O, F. In addition to the large spectroscopic amplitudes for
the s intruder configuration in the N=9 isotones,B and
C, significant s admixtures appear to occur in the
ground state of the neighbouring N=10 nuclei B and C. Similarly,
crossing the N=14 subshell, the occupation of the s orbital is
observed for O, F. Analysis of the longitudinal and transverse
momentum distributions reveals that both carry spectroscopic information, often
of a complementary nature. The general utility of high energy nucleon removal
reactions as a spectroscopic tool is also examined.Comment: 50 pages, 19 figures, submitted to Phys. Rev.
Coulomb breakup of neutron-rich Na isotopes near the island of inversion
First results are reported on the ground state configurations of the
neutron-rich Na isotopes, obtained via Coulomb dissociation (CD)
measurements as a method of the direct probe. The invariant mass spectra of
those nuclei have been obtained through measurement of the four-momentum of all
decay products after Coulomb excitation on a target at energies of
400-430 MeV/nucleon using FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated
Coulomb-dissociation cross-sections (CD) of 89 mb and 167 mb up to
excitation energy of 10 MeV for one neutron removal from Na and
Na respectively, have been extracted. The major part of one neutron
removal, CD cross-sections of those nuclei populate core, in its' ground state.
A comparison with the direct breakup model, suggests the predominant occupation
of the valence neutron in the ground state of Na and
Na is the orbital with small contribution in the
-orbital which are coupled with ground state of the core. The ground state
configurations of these nuclei are as Na_{gs (1^+)\otimes\nu_{s,d} and
Na, respectively. The ground state spin
and parity of these nuclei, obtained from this experiment are in agreement with
earlier reported values. The spectroscopic factors for the valence neutron
occupying the and orbitals for these nuclei in the ground state have
been extracted and reported for the first time. A comparison of the
experimental findings with the shell model calculation using MCSM suggests a
lower limit of around 4.3 MeV of the sd-pf shell gap in Na.Comment: Modified version of the manuscript is accepted for publication in
Journal of Physics G, Jan., 201
Crossing the Dripline to 11N Using Elastic Resonance Scattering
The level structure of the unbound nucleus 11N has been studied by 10C+p
elastic resonance scattering in inverse geometry with the LISE3 spectrometer at
GANIL, using a 10C beam with an energy of 9.0 MeV/u. An additional measurement
was done at the A1200 spectrometer at MSU. The excitation function above the
10C+p threshold has been determined up to 5 MeV. A potential-model analysis
revealed three resonance states at energies 1.27 (+0.18-0.05) MeV (Gamma=1.44
+-0.2 MeV), 2.01(+0.15-0.05) MeV, (Gamma=0.84 +-$0.2 MeV) and 3.75(+-0.05) MeV,
(Gamma=0.60 +-0.05 MeV) with the spin-parity assignments I(pi) =1/2+, 1/2- and
5/2+, respectively. Hence, 11N is shown to have a ground state parity inversion
completely analogous to its mirror partner, 11Be. A narrow resonance in the
excitation function at 4.33 (+-0.05) MeV was also observed and assigned
spin-parity 3/2-.Comment: 14 pages, 9 figures, twocolumn Accepted for publication in PR
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