Search results for "Photon spectra"
showing 5 items of 5 documents
Spectral distribution and Coulomb correction for nuclear bremsstrahlung induced by heavy targets
2021
Abstract Bremsstrahlung spectra below 250 MeV have been measured colliding 500 MeV–electrons with Cu, Ag, and Au targets. The experimental intensity ratios relative to Cu are well described by an accurate analytical high-energy theory, which accounts both for Coulomb distortion and screening. This represents the first experimental verification of the discovery by Bethe-Maximon that leading-order quantum mechanical calculations, equivalent to quasiclassical approximations, become exact at high energies and small angles. It also shows that radiative QED effects play a minor role in the covered part of the spectral distribution within the accuracy (1.6%) of the present measurements.
Evidence for thermal equilibration in multifragmentation reactions probed with bremsstrahlung photons
2001
The production of nuclear bremsstrahlung photons (E$_{\gamma}>$ 30 MeV) has been studied in inclusive and exclusive measurements in four heavy-ion reactions at 60{\it A} MeV. The measured photon spectra, angular distributions and multiplicities indicate that a significant part of the hard-photons are emitted in secondary nucleon-nucleon collisions from a thermally equilibrated system. The observation of the thermal component in multi-fragment $^{36}$Ar+$^{197}$Au reactions suggests that the breakup of the thermalized source produced in this system occurs on a rather long time-scale.
Rare decay η→ππγγ in chiral perturbation theory
1996
We investigate the rare radiative {eta} decay modes {eta}{r_arrow}{pi}{sup +}{pi}{sup {minus}}{gamma}{gamma} and {eta}{r_arrow}{pi}{sup 0}{pi}{sup 0}{gamma}{gamma} within the framework of chiral perturbation theory at {ital O}({ital p}{sup 4}). We present photon spectra and partial decay rates for both processes as well as a Dalitz contour plot for the charged decay. {copyright} {ital 1996 The American Physical Society.}
A time-of-flight facility for the measurement of electron-induced neutron spectra
1974
Abstract A time-of-flight facility is constructed to investigate photoneutrons in the energy range 5 MeV ≤ En ≤ 200 MeV. Photoneutrons are detected simultaneously at four angles (40.2°, 90°, 113.5°, 142.2°). The overall time resolution varies from 0.282 ns/m to 0.358 ns/m, depending on the different flight paths (18.56 m to 11.40 m). As a first check the facility is used to measure the ratio of the number of virtual photons to real photons via the photodisintegration of 2H. The measured values agree with the calculated photon spectra.
Ab initio study on the low-lying excited states of retinal
1997
Ab initio results for the electronic spectrum of all-trans-retinal and its truncated model 3-methyl-all-trans (10-s-cis)-2,4,6,8,10-undecapentaen-1-al are presented. The study includes geometry determination of the ground state. Vertical excitation energies have been computed using multiconfigurational second-order perturbation theory through the CASPT2 formalism. The lowest singlet excited state in gas phase is predicted to be of nπ∗ character. The lowest triplet state corresponds, however, to a ππ∗ state. The most intense feature of the spectrum is due to the strongly dipole-allowed ππ∗ transition, in accordance with the observed maximum in the one-photon spectra. The vertical excitation …