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The $^{103}\mathrm{Rh}$(n,${\mathit{n}}^{\ensuremath{'}}$${)}^{103}$${\mathrm{Rh}}^{\mathit{m}}$ cross section was measured by the activation method in the neutron energy range 5.7--12 MeV with an uncertainty of \ensuremath{\approxeq}5%. Monoenergetic neutrons produced by the D(d,n${)}^{3}$He reaction were used to irradiate metallic Rh samples at 0\ifmmode^\circ\else\textdegree\fi{} relative to the deuteron beam. The K x rays from $^{103}\mathrm{Rh}^{\mathit{m}}$ were measured with a calibrated Si detector, and the neutron fluence was determined by means of a $^{238}\mathrm{U}$ fission chamber. The measured cross sections resolve the discrepancies in previous data and agree with the results of recent statistical model calculations of the fast-neutron cross sections of rhodium. \textcopyright{} 1996 The American Physical Society.

The isomeric cross-section ratio ${\mathrm{\ensuremath{\sigma}}}_{\mathit{m}}$/(${\mathrm{\ensuremath{\sigma}}}_{\mathit{m}}$+${\mathrm{\ensuremath{\sigma}}}_{\mathit{g}}$) for the formation of $^{75}\mathrm{Ge}^{\mathit{m},\mathit{g}}$ was measured in $^{75}\mathrm{As}$(n,p), $^{78}\mathrm{Se}$(n,\ensuremath{\alpha}), and $^{76}\mathrm{Ge}$(n,2n) processes in the neutron energy range of 6.3 to 14.7 MeV. Use was made of the activation technique in combination with high-resolution \ensuremath{\gamma}-ray spectrometry. The ratio is relatively high (\ensuremath{\gtrsim}0.70) even at low incident particle energies and appears to increase only slightly with increasing energy. Statistical model calculations, taking into account precompound effects, were performed for the total reaction channel as well as for the isomer ratio. In either case, good agreement was obtained. For the investigated isomeric pair, no significant effect of reaction channels on the isomeric cross-section ratio was observed.

Cross sections of neutron-induced reactions on 103Rh have been calculated by means of the statistical model and the coupled-channels optical model for incident-neutron energies up to 30 MeV. The incentive for this study was a new measurement of the 103Rh(n,n′)103mRh cross section which will—together with the present calculations—enter into a dosimetry-reaction evaluation. The validation of the model parameters relied on nuclear-structure data as far as possible. Apart from the 103Rh(n,n′)103mRh excitation function also those for the 103Rh(n, 2n)102m,g,(m + g)Rh, 103Rh(n, 3n)101m,(m + g)Rh, 103Rh(n, p)103Ru and103Rh(n, α)100Tc reactions were calculated.

Reaction-model calculations of the cross sections of neutron-induced reactions on 23 Na have been carried out for incident energies up to 20 MeV. The work was mainly motivated by the interest in the 23 Na(n,2n) 22 Na reaction, for which conflicting experimental cross sections exist. The present study was aimed at the simultaneous description of the most recent data for the (n,2n) cross section together with the available experimental cross sections for other neutron-induced processes on 23 Na. The model parameters were determined from nuclear-structure information, as far as possible, and adjusted to reproduce the cross-section data.

It is demonstrated that (n,2n) cross sections for many medium-mass and heavy nuclei can be determined with high accuracy (≈3%) from existing data on nonelastic cross sections and energy-differentia...

A precision multidetector neutron time-of-flight (TOF) spectrometer and low-mass paral-lel-plate ionization chambers with a 252Cf deposit on the inner electrode are used to measure the spectral flu...

Excitation functions were measured for the {sup 90}Zr({ital n},{ital p}){sup 90}Y{sup {ital m}+{ital g}} and {sup 91}Zr({ital n},{ital p}){sup 91}Y{sup {ital m}+{ital g}} reactions over the neutron energy range of 6.5 to 10.6 MeV. Use was made of the activation technique in combination with radiochemical separation and low-level'' {beta}{sup {minus}} counting. From the available experimental data isomeric cross-section ratios were determined. Statistical model calculations taking into account precompound effects were performed for the formation of both the isomeric and ground states of the product. The calculational results on the total ({ital n},{ital p}) cross sections agree well with the experimental data. The measured and calculated cross sections for the formation of the isomeric states also agree up to an incident neutron energy of 10 MeV; at higher energies, however, the calculated values are appreciably higher. In the case of isomeric cross-section ratios good agreement was found between experiment and theory up to 10 MeV; at higher energies the calculated values are consistently higher.

The 23Na(n,2n)22Na cross section was measured at an incident energy of 19.45 MeV using the activation method. In addition, model calculations were performed aiming at reproduction of the new experimental value together with existing cross-section data for the (n,2n) reaction in the first 2.5 MeV above threshold as well as for other neutron-induced reactions on 23Na.

The spectra of emitted α-particles resulting from the reactions 64, 66, 68 Zn(p, α) 61, 63, 65 Cu at 15 MeV bombarding energy were measured at angles between 30° and 150°. The results are analyzed in the frame of the equilibrium and preequilibrium compound nucleus models. Back-shifted Fermi gas level density parameters for the relevant residual nuclei are deduced.

The energy and angular distributions of the protons from the 93Nb(n, xp) reactions were investigated by means of the Vienna multitelescope system. Whereas total hydrogen production cross sections a...

A revision of previous statistical model calculations of neutron-induced cross sections of 93 Nb for incident energies between 0.3 and 20 MeV was performed. The motivation for the revision was the publication of new experimental data which were partially in disagreement with the last version of calculations. The present work describes the extended base of experimental data and the adjustment of model parameters and compares the resulting calculated cross sections with the corresponding measured ones.

Neutron-induced reaction cross sections for 93 Nb for incident energies between 0.3 and 20 MeV were calculated by means of the single-channel optical model and a combination of pre-equilibrium and Hauser-Feshbach model. The parameters entering into these models were chosen or adjusted so as to reproduce a large amount of experimental data. A description of this fit procedure, the resulting calculated cross sections and their comparison to the experimental data are presented.

Special distribution methods have been used to make nuclear level-density calculations with full inclusion of two-body forces. The demands on computer time are large, however, and the information obtained in the very lowest energy region is not as extensive as would be desirable. We present calculations of the level density of $^{20}\mathrm{Ne}$ obtained with an alternative, but closely related, procedure based on the Lanczos algorithm. In addition, we discuss the possibility of accelerating the calculation of the moments for conventional spectral distribution calculations. Very encouraging results for both the Lanczos technique and the revised moment algorithm are obtained; some remaining problems are examined.

The energy and angular distribution of the α-particles from the reaction 93Nb+n for 14.1-MeV incident neutron energy was measured by means of a multitelescope system. The angle-integrated results are in good agreement with existing experimental α-production spectra at 14 and 15 MeV bombarding energy, and with calculations based on the statistical model of nuclear reactions including precompound processes and second-chance particle emission. For these calculations, a parameter set was employed with which the cross sections of other neutron-induced reactions on 93Nb can also be described. For α-energies above 12 MeV, where precompound processes dominate, our angular distributions show larger forward-backward asymmetries than predicted by the systematics of precompound angular distributions of Kalbach and Mann (1980, 1981).

An kollagenen Fasern des Coriums und der Subcutis wurde nach Behandlung mit Hyaluronidase sowie daran anschliesende Inkubation in Heparin bzw. Chondroitinsulfatlosung die v. Ebnersche Phenolreaktion mit Hilfe des Faktors\(\frac{{a + b}}{a}\) quantitativ ausgewertet und die Metachromasie beobachtet. Hierbei last sich nachweisen, das nach Einwirken von Hyaluronidase sowie nach Inkubation mit Heparin oder Chondroitinsulfat jene Gruppen des Kollagens, welche Phenol aufnehmen konnen, blockiert werden und somit der von uns zur Auswertung der Phenolreaktion an den kollagenen Fasern benutzte Faktor erniedrigt wird.

Discrepancies in the description of the neutron energy spectrum of Cf-252 above 5 MeV have given rise to an investigation of this part of the spectrum. The new PTB multi-angle neutron time-of-flight spectrometer and an improved version of the IRK lew mass ionization chamber were combined for the measurements. The influence of the detection efficiency for fission fragments on the neutron energy spectrum measured in coincidence with a TOF-detector was carefully studied. The measured spectra were corrected for background due to uncorrelated stops and for the efficiency of the fission chamber. The shape of the spectrum is best described in the energy range 3 MeV ≤ En ≤ 13 MeV by a Maxwellian distribution with the temperature parameter Eo = 1.355 MeV.

For neutrons incident on 52Cr, 55Mn, 56Fe and 58,60Ni, total cross sections, differential elastic cross sections, production spectra of emitted particles and photons integrated over solid angle, production cross sections of solid and gaseous transmutation products were calculated for neutron energies up to 30 MeV. For the calculations, the optical model, the compound nucleus model and the exciton model were employed, considering in the precompound stage the emission of neutrons, protons and α-particles, in the compound nucleus stage the emission of these particles and of photons. The dependence of the calculated cross sections on the model parameters was studied. A consistent set of parameters was chosen so as to achieve an overall best fit to all experimental cross section data which, however, exist mainly for incident energies below 20 MeV.

Average s-wave resonance spacings were derived from high-resolution proton resonance data for 11 odd-Z nuclei in the mass range A = 41--67 and compared with the average s-wave spacings obtained from neutron resonances for their odd-N isobars. After careful correction for missing levels the neutron and proton results are consistent; proton resonance data can be used to increase the data base for nuclear level densities. After correction to a common excitation energy, the spacings show a correlation with the shell correction energy E/sub shell/, especially for A = 41, 55, and 59, where data exist for three isobars with quite different shell correction energies. The dependence of the average level spacing D-bar on E/sub shell/ is approximately exponential, in good agreement with the theoretical models of Ignatyuk et al. and Kataria et al. The data also have been used to calculate asymptotic a parameters in these two models. The mass dependence of these parameters can be described by the simple relation a = 0.137A with an rms deviation of 4.3%. Attempts to describe the data within the Fermi gas model resulted in much larger fluctuations of the parameters with A and Z. Finally, the data were compared to the predictions more » of the microscopic Fermi gas model, using the single particle level scheme of Seeger and Perisho. At present, the quality of this description is still somewhat worse than with the phenomenological models of Ignatyuk et al. and Kataria et al. « less

The energy and angular distribution of secondary neutrons from the interaction of 14-MeV neutrons with sodium and natural lead were investigated. Absolute double-differential neutron emission cross sections were measured for reaction angles from 30{degree} to 150{degree} in steps of 15{degree} in the secondary neutron energy range 2{endash}14 MeV using the time-of-flight facility at the Institut f{umlt u}r Radiumforschung und Kernphysik, Vienna. Systematic uncertainties in these measurements could be reduced to less than 3{endash}5{percent} (depending on secondary neutron energy) resulting in total uncertainties of less than 5{percent} for a large part of the studied range in angle and energy for Pb and of less than 8{percent} for Na. These results agree with previous measurements within the relatively large uncertainties of the latter. The measured cross sections were compared to the results of statistical model calculations using the quantum mechanical theory of Feshbach, Kerman, and Koonin for preequilibrium emission and also with calculations based on the exciton model and the Kalbach-Mann systematics for the shape of the angular distributions. For compound nucleus decay, the Hauser-Feshbach model was used in both cases. Very good agreement was found with both predictions in the case of lead; in the case of sodium, noticeable discrepancies do more » show the limits of applicability of any statistical model for light nuclei. {copyright} {ital 1997} {ital The American Physical Society} « less

A recent paper compared moment method and Lanczos method calculations of the level density of20Ne. The present work extends this comparison to include a new type of Lanczos expansion. This expansion procedure shares the advantage of the traditional Lanczos method of a positive definite level density, but unlike the latter, may be used in an essentially infinite basis. Calculations utilizing dsdf and ppdsd bases have been compared with experimental values for the level density, parity ratio and spin cutoff parameters to determine the appropriateness of the input parameters and the model, while calculations in a dsd basis are compared with exact calculated results to test the accuracy of representation provided by the expansion technique.