The 139La(n, ? ) cross section: Key for the onset of the s-process

The nuclear resonance parameters and the capture cross section of the neutron magic isotope 139La has been measured relative to 197Au in the energy range of 0.6 eV-9 keV at the neutron time-of-flight (n_TOF) facility at CERN. The description of the experimental apparata is followed by the a discussion on the data analysis procedures consisting in the efficiency correction by means of the Pulse Height Weighting Function technique, in the determination of different background components and in their subtraction. The resonance parameters have been extracted together with the main nuclear quantities such as the resonance integral, RI = 10.8 ? 1.0 barn and the average &#947;-widths for the s-waves (GAMMAgamma)l=0 = 51.6 ? 5.4 meV, and for p-waves (GAMMAgamma)l=1= 32.8 ? 6.9 meV. The n_TOF data allowed also the calculations of the nuclear level densities (D)l=0= 268 ? 22 eV, (D)l=1< 250 eV and of the neutron strength function S0 = (0.78 ? 0.04)?10&#8211;4, S1 = (0.72 ? 0.05)?10&#8211;4. These results improve the accuracy of the existing data. The deduced values of the Maxwellian-averaged capture cross section, together with the most recent spectroscopic observations in low metallicity stars, open new scenarios for modelling the nucleosynthesis and the chemical evolution of heavy nuclei in the Galaxy.

Authors:

TERLIZZI R., ABBONDANNO U., AERTS G., ALVAREZ H, ALVAREZ-VELARDE F., ANDRIAMONJE S., ANDRZEJEWSKI J., ASSIMAKOPOULOS P., AUDOUIN L., BADUREK G., BAUMANN P., BECVAR F., BERTHOUMIEUX E., CALVIANI M., CALVINO F., CANO-OTT D., CAPOTE R., CARRILLO DE ALBORNOZ A., CENNINI P., CHEPEL V., CHIAVERI E., COLONNA N., CORTES G., COUTURE A., COX J., DAHLFORS M., DAVID S., DILLMANN I., DOLFINI R., DOMINGO-PARDO C., DRIDI W., DURAN I., ELEFTHERIADIS C., EMBID-SEGURA M., FERRANT L., FERRARI A., FERREIRA-MARQUES R., FITZPATRICK L., FRAIS-KOELBL H, FUJII K., FURMAN W., GALLINO R., GONCALVES I., GONZALEZ-ROMERO E., GOVERDOVSKI A., GRAMEGNA F., GRIESMAYER E, GRIESMAYER E, GUERRERO C, GUNSING F., HAAS B., HAIGHT R., HEIL M., HERRERA-MARTINEZ A., IGASHIRA M., ISAEV M., JERICHA E., KADI Y., KAPPELER F., KARAMANIS D., KARADIMOS D., KERVENO M., KETLEROV V., KOEHLER P., KONOVALOV V., KOSSIONIDES E., KRTICKA M., LAMBOUDIS C., LEEB H., LINDOTE A., LOPES I., LOZANO M., LUKIC S., MARGANIEC J., MARQUES L., MARRONE S., MASSIMI C., MASTINU P., MENGONI A., MILAZZO P.M., MOREAU C., MOSCONI M., NEVES F., OBERHUMMER H., O?BRIEN S., PANCIN J., PAPACHRISTODOULOU C., PAPADOPOULOS C., PARADELA C., PATRONIS N., PAVLIK A., PAVLOPOULOS P., PERROT L., PIGNATARI M., PLAG R., PLOMPEN Arjan, PLUKIS A., POCH A., PRETEL C., QUESADA J., RAUSCHER T., REIFARTH R., ROSETTI M., RUBBIA C., RUDOLF G., RULLHUSEN P., SALGADO J., SARCHIAPONE L., SAVVIDIS I., STEPHAN C., TAGLIENTE G., TAIN J. L., TASSAN-GOT L., TAVORA L., VANNINI G., VAZ P, VENTURA A., VILLAMARIN D., VINCENTE M. C., VLACHOUDIS V., VLASTOU R., VOSS F., WALTER S., WENDLER H., WIESCHER M., WISSHAK K.

Publisher:

AMER PHYSICAL SOC

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Printed