1,504 research outputs found
Deuteron Elastic Scattering from He3 and H3
The elastic scattering of deuterons from He3 and H3 has been studied for bombarding energies up to 11 MeV. The excitation curves obtained show a broad resonance in the scattering cross section corresponding to an excitation energy of 20±0.5 MeV in both He5 and Li5. These data, together with H3(d, n)He4 and He3(d, p)He4 data from other sources, tend to indicate that D waves are responsible for the anomaly
Formation of even-numbered hydrogen cluster cations in ultracold helium droplets
Neutral hydrogen clusters are grown in ultracold helium nanodroplets by successive pickup of hydrogen molecules. Even-numbered hydrogen cluster cations are observed upon electron-impact ionization with and without attached helium atoms and in addition to the familiar odd-numbered H(n)(+). The helium matrix affects the fragmentation dynamics that usually lead to the formation of overwhelmingly odd-numbered H(n)(+). The use of high-resolution mass spectrometry allows the unambiguous identification of even-numbered H(n)(+) up to n congruent to 120 by their mass excess that distinguishes them from He(n)(+), mixed He(m)H(n)(+), and background ions. The large range in size of these hydrogen cluster ions is unprecedented, as is the accuracy of their definition. Apart from the previously observed magic number n = 6, pronounced drops in the abundance of even-numbered cluster ions are seen at n = 30 and 114, which suggest icosahedral shell closures at H(6)(+)(H(2))(12) and H(6)(+)(H(2))(54). Possible isomers of H(6)(+) are identified at the quadratic configuration interaction with inclusion of single and double excitations (QCISD)/aug-cc-pVTZ level of theory (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3035833
The projective translation equation and unramified 2-dimensional flows with rational vector fields
Let X=(x,y). Previously we have found all rational solutions of the
2-dimensional projective translation equation, or PrTE,
(1-z)f(X)=f(f(Xz)(1-z)/z); here f(X)=(u(x,y),v(x,y)) is a pair of two (real or
complex) functions. Solutions of this functional equation are called projective
flows. A vector field of a rational flow is a pair of 2-homogenic rational
functions. On the other hand, only special pairs of 2-homogenic rational
functions give rise to rational flows. In this paper we are interested in all
non-singular (satisfying the boundary condition) and unramified (without
branching points, i.e. single-valued functions in C^2\{union of curves})
projective flows whose vector field is still rational. We prove that, up to
conjugation with 1-homogenic birational plane transformation, these are of 6
types: 1) the identity flow; 2) one flow for each non-negative integer N -
these flows are rational of level N; 3) the level 1 exponential flow, which is
also conjugate to the level 1 tangent flow; 4) the level 3 flow expressable in
terms of Dixonian (equianharmonic) elliptic functions; 5) the level 4 flow
expressable in terms of lemniscatic elliptic functions; 6) the level 6 flow
expressable in terms of Dixonian elliptic functions again. This reveals another
aspect of the PrTE: in the latter four cases this equation is equivalent and
provides a uniform framework to addition formulas for exponential, tangent, or
special elliptic functions (also addition formulas for polynomials and the
logarithm, though the latter appears only in branched flows). Moreover, the
PrTE turns out to have a connection with Polya-Eggenberger urn models. Another
purpose of this study is expository, and we provide the list of open problems
and directions in the theory of PrTE; for example, we define the notion of
quasi-rational projective flows which includes curves of arbitrary genus.Comment: 34 pages, 2 figure
p-He^4 Final-State Interaction in He^3(He^3, 2p)He^4
The He^3(He^3, 2p)He^4 reaction, leading to a three-body
final state consisting of an alpha particle and two protons, has been investigated at bombarding energies
from 3 to 18 MeV using a He^3 beam from the ONR-CIT
tandem accelerator. The motivation for this work
has been twofold; to gain an understanding of the reaction
mechanism over a wide range of bombarding energy and to develop a consistent method for determining the total reaction cross section that can be extended to lower bombarding energies. What follows is a
preliminary report dealing with general features of the
experimental results
Scattering of He3 from He3
The elastic scattering of He3 particles from a He3 target has been investigated for bombarding energies between 3 and 12 MeV. Excitation curves were obtained for center-of-mass scattering angles 30.6°, 54.8°, 70.1°, and 90°; and angular distributions were measured at bombarding energies of 3.03, 5.90, 7.91, 9.92, and 11.93 MeV. The excitation curves are without structure and all decrease with increasing energy in a smooth, monotonic fashion. The five angular distributions exhibit marked disagreement with theoretical predictions based on the resonating group structure method
Studies of Pi° Production Near Threshold
Supported by the National Science Foundation and Indiana Universit
Atomic Alchemy
We consider the transitions between electromagnetic bound states, such as the
exclusive weak decay of a muonic atom into an electronic atom: We show that relativistic effects in the
atomic wavefunctions are crucial for determining the rate. In the case of heavy
atoms, the exclusive channel branching ratios exceed possibly
bringing the study of these rare decays within experimental reach. Such
processes thus provide a detailed laboratory for studying the high momentum
tail of wavefunctions in atomic physics; in addition, they provide a simple toy
model for investigating analogous exclusive heavy hadronic decays in quantum
chromodynamics such as Comment: 16 pages and 5 Figures, SLAC-PUB-648
Nuclear recoil effect on the magnetic-dipole decay rates of atomic levels
The effect of finite nuclear mass on the magnetic-dipole transition
probabilities between fine-structure levels of the same term is investigated.
Based on a rigorous QED approach a nonrelativistic formula for the recoil
correction to first order in m_e/M is derived. Numerical results for
transitions of experimental interest are presented.Comment: 9 page
Roper excitation in reactions
We calculate differential cross sections and the spin transfer coefficient
in the reaction for proton
bombarding energies from 1 to 10 GeV and invariant masses spanning
the region of the N(1440) Roper resonance. Two processes --
excitation in the -particle and Roper excitation in the proton -- are
included in an effective reaction model which was shown previously to reproduce
existing inclusive spectra. The present calculations demonstrate that these two
contributions can be clearly distinguished via , even under kinematic
conditions where cross sections alone exhibit no clear peak structure due to
the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late
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