Recoilless

Gun powders/propcl hints Muzzle blast Recoilless rifle blast Exploding sparks Exploding wires Laser sparks Contained explosions ... 

Ontos. Designated as the M-50, this US Marine Corps system is a full-track self-propelled direct-fire and antitank weapon. It is aimed with six 106mm recoilless rifles, one. 30cal machine gun, and four. SOcal spotting rifles. It has a top speed of 40mph and a crew of three Ref J. Quick, Dictionary of Weapons and Military Terms , McGraw-Hill, NY (1973), 334... 

Pressures, Gun. Pressures within a gun tube or barrel, a used in design practices. Because of the wide variations in size, wall ratios, heat dissipation, required safety actors, etc, design practices, vary for the different types of weapons. Some pressure terms have significance in the design of (a) all tubes and barrels, (b) cannon tubes, (c) recoilless rifle tubes, and (d) small arms, barrels, viz ... 

Rare-earth ions inserted in the tetraborides have the 34- oxidation state, except for CeB4 and YbB4 (see Fig. 2). The abnormal volume contraction for the CeB4 unit cell can be explained by the presence of some Ce ions . Recoilless y-ray emission spectra and magnetic measurements indicate that ytterbium in YbB4 has an intermediate valence state as in YbAl3... 

The rare earths in their dodecaborides have the 3 + oxidation state except for Yb and Tm which have an intermediate valence state. A recoilless y-ray emission spectrum study of TmB,2 shows no magnetic ordering at 1.35 K the spectra of YbB,2 reveal no magnetic structure to 1.35 K. The compounds HoB,2, ErB,2 order antiferromagnetically, and ZrB,2 and LuB,2 become superconducting < 5.8 K and < 0.48 K, respectively. ... 

Chemical bonding and dynamic properties of Au clusters are obtained by recoilless y-ray spectroscopy and- P NMR investigations - . ... 

The Mossbauer effect can only be detected in the solid state because the absorption and emission events must occur without energy losses due to recoil effects. The fraction of the absorption and emission events without exchange of recoil energy is called the recoilless fraction, f. It depends on temperature and on the energy of the lattice vibrations /is high for a rigid lattice, but low for surface atoms. 

Mossbauer effect spectroscopy, MES, Is based on the ability of certain nuclei to undergo recoilless emission and absorption ofY rays (16). The energy and multiplicity of the ground and excited states of a given nucleus are modified by the chemical environment. It Is thus most often necessary to compensate for the differences In... 

However, in contrast, the resonance effect increased by cooling both the source and the absorber. Mdssbauer not only observed this striking experimental effect that was not consistent with the prediction, but also presented an explanation that is based on zero-phonon processes associated with emission and absorption of y-rays in solids. Such events occur with a certain probability/, the recoil-free fraction of the nuclear transition (Sect. 2.4). Thus, the factor/is a measure of the recoilless nuclear absorption of y-radiation - the Mdssbauer effect. 

Fig. 2.6 Schematic illustration of a Mossbauer transmission experiment in five steps. The Absorption bars indicate the strength of recoilless nuclear resonant absorption as determined by the overlap of emission and absorption lines when the emission line is shifted by Doppler modulation (velocities Uj,. .., 1)5). The transmission spectrum T v) is usually normalized to the transmission T oo) observed for v oo by dividing T(v)IT(oo). Experimental details are found in Chap. 3...

We are interested in the transmission of y-quanta through the absorber as a function of the Doppler velocity. The radiation is attenuated by resonant absorption, in as much as emission and absorption lines are overlapping, but also by mass absorption due to photo effect and Compton scattering. Therefore, the number Tt E2)AE of recoilless y-quanta with energies EXo E + AE traversing the absorber is given by... 

Fig. 3.19 Schematic illustration of the measurement geometry for Mossbauer spectrometers. In transmission geometry, the absorber (sample) is between the nuclear source of 14.4 keV y-rays (normally Co/Rh) and the detector. The peaks are negative features and the absorber should be thin with respect to absorption of the y-rays to minimize nonlinear effects. In emission (backscatter) Mossbauer spectroscopy, the radiation source and detector are on the same side of the sample. The peaks are positive features, corresponding to recoilless emission of 14.4 keV y-rays and conversion X-rays and electrons. For both measurement geometries Mossbauer spectra are counts per channel as a function of the Doppler velocity (normally in units of mm s relative to the mid-point of the spectrum of a-Fe in the case of Fe Mossbauer spectroscopy). MIMOS II operates in backscattering geometry circle), but the internal reference channel works in transmission mode...

In the context of the inelastic scattering process that is the basis for NIS, one observes inelastic transitions g) a ) k) a + A a ), where g)and c) are the ground and the excited states of the nucleus. Thus, the transition energies shifted from the recoilless absorption ( o) as = q + X) In terms of the normal-... 

Nii ,Pd ,(x 0-0.995) Absorber recoilless fraction, energy shift, and as function of x 5 values from temperature dependence of SOD calculation of and comparison with measurements in applied fields... 

Conroy and Perlow [235] have measured the Debye-Waller factor for W in the sodium tungsten bronze Nao.gWOs. They derived a value of/= 0.18 0.01 which corresponds to a zero-point vibrational amplitude of R = 0.044 A. This amplitude is small as compared to that of beryllium atoms in metallic beryllium (0.098 A) or to that of carbon atoms in diamond (0.064 A). The authors conclude that atoms substituting tungsten in bronze may well be expected to have a high recoilless fraction. 

It is a matter of historical interest that Mossbauer spectroscopy has its deepest root in the 129.4 keV transition line of lr, for which R.L. Mossbauer established recoilless nuclear resonance absorption for the first time while he was working on his thesis under Prof. Maier-Leibnitz at Heidelberg [267]. But this nuclear transition is, by far, not the easiest one among the four iridium Mossbauer transitions to use for solid-state applications the 129 keV excited state is rather short-lived (fi/2 = 90 ps) and consequently the line width is very broad. The 73 keV transition line of lr with the lowest transition energy and the narrowest natural line width (0.60 mm s ) fulfills best the practical requirements and therefore is, of all four iridium transitions, most often (in about 90% of all reports published on Ir Mossbauer spectroscopy) used in studying electronic stractures, bond properties, and magnetism. 

The recoilless nuclear resonance absorption of y-radiation (Mossbauer effect) has been verified for more than 40 elements, but only some 15 of them are suitable for practical applications [33, 34]. The limiting factors are the lifetime and the energy of the nuclear excited state involved in the Mossbauer transition. The lifetime determines the spectral line width, which should not exceed the hyperfine interaction energies to be observed. The transition energy of the y-quanta determines the recoil energy and thus the resonance effect [34]. 57Fe is by far the most suited and thus the most widely studied Mossbauer-active nuclide, and 57Fe Mossbauer spectroscopy has become a standard technique for the characterisation of SCO compounds of iron. 

In a subsequent measurement at a potential of -0.9 V, the resonant absorption of the doublet underwent a marked drop, an effect that may be due to an increase in the solubility of the oxide, and thus in a loss of solid in the electrode, and/or to a modification in the recoilless fraction of the solid induced by the hydration of the lattice. 

The Mossbauer effect involves the resonance fluorescence of nuclear gamma radiation and can be observed during recoilless emission and absorption of radiation in solids. It can be exploited as a spectroscopic method by observing chemically dependent hyperfine interactions. The recent determination of the nuclear radius term in the isomer shift equation for shows that the isomer shift becomes more positive with increasing s electron density at the nucleus. Detailed studies of the temperature dependence of the recoil-free fraction in and labeled Sn/ show that the characteristic Mossbauer temperatures Om, are different for the two atoms. These results are typical of the kind of chemical information which can be obtained from Mossbauer spectra. 

Results obtained from the alkali iodides on the isomer shift, the NMR chemical shift and its pressure dependence, and dynamic quadrupole coupling are compared. These results are discussed in terms of shielding by the 5p electrons and of Lbwdins technique of symmetrical orthogonalization which takes into account the distortion of the free ion functions by overlap. The recoilless fractions for all the alkali iodides are approximately constant at 80°K. Recent results include hybridization effects inferred from the isomer shifts of the iodates and the periodates, magnetic and electric quadrupole hyperfine splittings, and results obtained from molecular iodine and other iodine compounds. The properties of the 57.6-k.e.v. transition of 1 and the 27.7-k.e.v. transition of 1 are compared. 

---