Resonance Absorption Of Gamma Rays Research Articles

Initial studies of the gamma resonance of the 109m Ag isomer with a gravitational gamma spectrometer

The problem of observing the Mossbauer resonance absorption of gamma rays from long-lived isomers is briefly outlined, first and foremost for 109m Ag taken as an example. Experiments indicative of a small broadening of the Mossbauer gamma line of this isomer in metallic silver are described. This circumstance made it possible to develop and manufacture a gravitational gamma spectrometer and to perform the first experiments with it, which confirm once again the previous data on a small width of the gamma line in question. The broadening factor obtained from these data proved to be 6.3 −1.9 +5.2 .

A method for detection of explosives based on nuclear resonance absorption of gamma rays in 14N

The physical principles the of Nuclear Resonance Absorption (NRA) method and its application to explosives detection are described. In this method, the object to be tested is scanned by a beam of 9.17 MeV gamma rays which undergoes resonant attenuation whenever the beam encounters regions of nitrogen concentration. This resonant component of attenuation is detected using an array of gamma ray detectors containing a nitrogen-rich medium. From the reconstructed spatial distribution of nitrogen density obtained in multi-view scanning, the presence of an explosive can be determined.

A rising war on terrorists

Technology for detecting and preventing acts of terrorism is addressed. Attention is directed toward methods for detecting explosives. The one technology, thermal-neutron activation (TNA), that has so far proven that it can quickly and reliably detect specified quantities of explosives within luggage and divert suspect bags without human intervention is described. Promising alternatives to TNA, which is very expensive, are resonance absorption of gamma rays and fast neutron activation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Resonant emission of secondary electrons associated with recoilless nuclear absorption of gamma rays in solids

Secondary electrons generated in polycrystalline iron samples due to nuclear resonant absorption of 14.4 keV gamma-rays in 57Fe and subsequent reemission of internal conversion and Auger electrons were investigated for an energy range between 0 and 100 eV with a cylindrical mirror analyzer. It was found that the resonance absorption of gamma-rays is accompanied by an intensive emission of secondary electrons, particularly at energies about 5–10 eV. It was shown that those electrons can be utilized for more efficient registration of conversion electron Mössbauer spectra due to their large collection and detection efficiency in equipment using channel electron multipliers.

Simulation of resonance absorption of gamma rays by the Monte Carlo method

Simulation of resonance absorption of gamma rays by the Monte Carlo method

Resonance Detectors for Mossbauer Experiments

The Mössbauer effect can be observed by detecting the gamma rays or the internal-conversion electrons and X-rays that are emitted in the de-excitation of nuclei excited previously by the resonance absorption of gamma rays. The use of conversion electrons for recording the resonance absorption is limited by the short range of these electrons. However, in special detectors--gas proportional and thin plastic scintillators--where the absorber is an integral part of the device, the detection can be made quite efficiently. In this paper the properties (counting efficiency, background, and line shape) of these resonance detectors will be discussed and compared with experimental data. It will be shown that in certain geometrical configurations the line width can be reduced whereas its shape remains very close to the Lorentzian. The detector used in this experiment is a flat gasflow proportional detector in which the cathode surface is coated with iron enriched in the isotope Fe57. The relative merits of the different detection systems will be discussed briefly.

Lattice Dynamical Aspects of the Resonance Absorption of Gamma Rays by Nuclei Bound in a Crystal

Modifications of the lattice vibrations caused by an impurity nucleus in a host crystal and their effects on the absorption spectrum of the perfect host crystal are discussed. The no-phonon,'' or Mossbauer, absorption cross section, the one-phonon'' absorption cross section, and the secondorder Doppler shift are discussed in resonant absorption of gamma rays by nuclei in crystals. 61 references. (R.E.U.)

Resonance Absorption of Gamma Rays in Normal and Superconducting Tin

A study of the resonant absorption of the 23.8-keV gamma rays in ${\mathrm{Sn}}^{119}$ has been made between 373 and 1.1\ifmmode^\circ\else\textdegree\fi{}K by using the ${\mathrm{Sb}}^{119}$ $K$-capture parent. The source was prepared by bombarding natural Sn with 10-MeV deuterons in a cyclotron, and was thick enough to absorb resonantly a large portion of the recoilless photons emitted. By studying the self-absorption in this source between 373 and 60\ifmmode^\circ\else\textdegree\fi{}K and taking into account the contributions to the intensity due to resonant scattering, an average value of the Debye temperature $\ensuremath{\theta}$ has been derived. In order to see if the phonon spectrum undergoes a change in passing from the superconducting to the normal phase, the counting rate was measured at several temperatures between 4.2 and 1.1\ifmmode^\circ\else\textdegree\fi{}K, with and without a magnetic field strong enough to destroy the superconductivity of the source. Using the derived value of 140\ifmmode^\circ\else\textdegree\fi{}K for $\ensuremath{\theta}$, it was concluded that the change in $\ensuremath{\theta}$ between the two phases could not be more than 0.76\ifmmode^\circ\else\textdegree\fi{}K.

Nuclear Resonance Absorption of Gamma Rays at Low Temperatures

Recent experiments by Mossbauer have shown that nuclear resonance absorption of gamma rays can take place when both source and absorber are placed at liquid nitrogen temperature. The source used in his measurements was Os/sup 191/ which decays to Ir/sup 191/with a 16-day haif life. This beta decay populates a 4.9-sec isomeric state which cascades through the 129-kev excited state of this nucleus. The present experiment was designed to measure the lifetime of this excited state. (W.D.M.)