B V Thirumala Rao

Activation Cross-Sections for 14.2 MeV Neutrons on Molybdenum

Using the activation method, the cross-section for the following reactions on molybdenum were measured employing the mixed powder technique and Ge(Li) gamma-ray spectroscopy: 94Mo(n, 2n)93mMo, 3.5 ± 0.5 mbarn; 92Mo(n, 2n)91mMo, 19 ± 3 mbarn; 92Mo(n, 2n)91m+gMo, 226 ± 11 mbarn; 100Mo(n, p)100m2Nb, 9 ± 1 mbarn; 98Mo(n, p)98Nb, 10 ± 1 mbarn; 97Mo(n, p)97mNb, 5 ± 1 mbarn; 96Mo(n, p)96Nb, 12 ± 2 mbarn; 92Mo(n, α)89mZr, 2.1 ± 0.5 mbarn; and 92Mo(n, α)89m+gZr; 24 ± 6 mbarn; the neutron energy was 14.2 ± 0.2 MeV. The experimental cross-sections were compared with the predictions of evaporation model and of different versions of pre-equilibrium model. The master equation approach appears to give satisfactory results.

Neutron activation cross sections in some barium isotopes at 14.2 MeV

Activation cross sections were measured for the reactions 136Ba(n,2n)135mBa, 138Ba(n,p)138Cs and 138Ba(n, alpha )135m,gXe at an incident neutron energy of 14.2+or-0.2 MeV using the mixed powder technique. A high-resolution Ge(Li) detector was used to measure the induced gamma-ray activities. The cross sections were compared with both experimental and theoretical values reported in the literature.

Neutron induced reactions in antimony isotopes at 14 MeV

Neutron activation cross-sections in antimony isotopes were measured at an incident neutron energy of 14.2±0.2 MeV. The versatile mixed powder technique and high resolution Ge(Li) detector gamma ray spectroscopy were employed. The measured cross-sections were compared with those reported in literature. The total (n, 2n) cross-sections were compared with the estimates based on statistical theory. The experimental values were found to be smaller than the statistical theory estimates and the resulting diminution was attributed to the precompound effects in (n, 2n) reactions at 14 MeV.

Ge(Li) measurement of some neutron activation cross-sections at (14.2±0.2) MeV

SummaryPrecision measurements of activation cross-sections were made for the reactions138Ba(n, 2n)137Bam,167Er(n, p)167Ho and181Ta(n, 2n)180Tam at an incident-neutron energy of (14.2±0.2) MeV. The mixed-powder technique and high-resolution Ge(Li) detector coupled to a ND 512 channel analyser system were employed. The cross-section values were compared with the values reported in the literature.RiassuntoSono state fatte precise misurazioni delle sezioni d’urto d’attivazione per le reazioni138Ba(n, 2n)137Bam,167Er(n, p)167Ho e181Ta(n, 2n)180Tam a un’energia del neutrone incidente di (14.2±0.2) MeV. Sono state impiegate la tecnica della miscela di polveri e un rivelatore a Ge(Li) ad alta risoluzione accoppiato a un sistema analizzatore ND a 512 canali. Si confrontano i valori delle sezioni d’urto con quelli riportati nella letteratura.РезюмеПроводятся точные измерения поперечных сечений активации для реакций138Ba(n, 2n)137Ba,167Er(n, p)167Ho и181Ta(n, 2n)180Tam при энергии падающего нейтрона (14.2±0.2) МэВ. Используется Ge(Li) детектор с высоким разрешением, связанный с ND 512 канальным анализатором. Полученные поперечные сечения сравниваются с результатамич имеющимися в литературе.

Anomalous conversion in the decay of197mHg

The total andK-shell conversion coefficients of the 165 keV transition in the decay of197mHg are determined from intensity balance considerations and a coincidence technique using a Ge(Li)—NaI (Tl) system respectively. The resultant values areaT=274.8±19.2 andaK=47±12, whil the corresponding theoretical values are 344 and 77 respectively, indicating anomalous conversion. The gamma ray transition probability however, shows a hindrance of only about 6 and cannot be correlated with the present anomalous conversion data. TheK/L ratio of the 130 keV transition, determined using a summing method with a Ge(Li) detector, yielded 0.090±0.012, while the corresponding theoretical value is 0.048, indicating anomalous conversion. The corresponding gamma transition probability shows a hindrance of about 3000, in correlation with anomalous conversion.

Radioactive decay of 91mNb

The radioactive decay of 91mNb, produced by the reaction 89Y( alpha ,2n), is studied using Ge(Li), HPGe and Si(Li) detectors. The K-conversion coefficient, alpha K, of the 104.5 keV transition is determined accurately, for the first time, from the Nb Kalpha X-ray and 104.5 keV gamma-ray intensities. The experimental value of alpha K thus determined is 115(5), in agreement with the value expected for an M4 transition.

Conversion of the 42 keV transition in the decay of191Os

SummaryThe total as well as theL-conversion coefficient of the 42 keV transition in the decay of191Os are determined from intensity balance considerations and XPG technique, respectively, using a 3 mm Si(Li) detector system. The resultant values are αT = 13709 (1900), αL = 11700 (2100). The present total conversion coefficient shows good agreement within the uncertainty limits, with the value αT = 13.500−5200+21100 reported by Lange, whereas theL-conversion coefficient is reported for the first time. Our present values are also compared with the theoretical values interpolated from the tables of Hager and Seltzer and of Roselet al.RiassuntoSi determinano il coefficiente totale e quello di conversioneL della transizione a 42 keV nel decadimento di191Os considerando il bilancio d’intensità e la tecnica XPG, rispettivamente, usando un sistema di rivelatori a 3 mm Si(Li). I valori risultanti sono αT = 13709 (1900), αL = 11700 (2100). Il coefficinete di conversione totale è in buon accordo, entro i limiti di incertezza, con il valore αT = 13.500−5200+21100 riportato da Lange, mentre il coefficiente di conversioneL è riportato per la prima volta. I nostri valori attuali sono anche confrontati con i valori teorici interpolati dalle tavole di Hager e Seltzer e di Roselet al.