Bulletin #13 March 05, 2001 _/ _/ _/ _/_/_/_/ _/_/_/_/ _/_/ _/_/ _/_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/_/_/_/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/ _/_/_/_/ _/_/_/_/ ATOMIC MASS DATA CENTER -------------------------------------------------------------------- I - NEWS FROM EXPERIMENTS ON MASSES The MISTRAL experiment / Celine Monsanglant March 2001 MISTRAL is an on-line transmission and radiofrequency spectrometer installed at ISOLDE. Mass measurements are derived from the determination of the cyclotron frequency of the ion turning in an homogeneous magnetic field compared to that of a reference ion. This method allows very fast and precise mass measurements (a few 10 -7). Mass measurements of 25Ne, 26Ne and the very short-lived nuclide 32Mg (95 ms) have been performed in 1999. The analysis has been rendered more complex by the presence of many isobars in the radioactive beam. MISTRAL values for these three nuclides are more precise and carry the highest weight in the new average. The mass of 32Mg is 280 keV more bound than in the tables. The intensity of the deformation is thus reinforced in this region of neutron-rich N=20 nuclides. Comparisons to classical models in nuclear physics (shell models, Mean field models, etc.) have also been studied. These results are from C. Monsanglant's thesis (Orsay, October 2000) http://csnwww.in2p3.fr/AMDC/experimental/th-monsangl.pdf (full text in French), and th-monsangl-sum.pdf (English 1/2 page summary). Recent results from MISTRAL are given this week at NP2001, see preprint http://csnwww.in2p3.fr/AMDC/experimental/gottingen.pdf Schottky Mass Spectrometry / Markus Falch February 2001 Schottky Mass Spectrometry at the experimental storage ring ESR of the GSI is an effective tool for systematic mass measurements of exotic nuclei which is based on the detection of the revolution frequencies of highly-charged ions which are stored and cooled in the storage ring ESR. The method has been significantly improved by a new data aquisition system (TCAP) which yields several advantages for the data analysis. During a beamtime of two weeks in November 1997 this system was used for the first time for systematic mass measurements of exotic nuclei at the ESR of the GSI. In the experiment, masses of 346 neutron-deficient nuclei in the region of Rh to Po with half-lives > 5 s have been measured containing 152 nuclei with previously unknown mass values or with large mass errors. Due to alpha-chains with known Qalpha values linked to the region of measured masses, the determination of 88 additional nuclei with half-lives down to milliseconds was possible. Between Lu and Pa these proton-rich nuclei reach the proton-dripline. With the new TCAP-system a mass resolution of 1.8e-6 has been achieved. This corresponds to errors of (10-250) keV and allows the resolution of isomeric states. The systematic error, 16.2 keV, has been reduced by a factor of 5.7 compared to former Schottky mass measurements. These results are part of M. Falch's thesis (Munich, October 2000), available at the AMDC: http://csnwww.in2p3.fr/AMDC/experimental/ th-falch.pdf for the full text in German, and th-falch-sum.pdf for an English 2 pages summary. II - NEWS FROM THEORIES ON MASSES Calculated Masses for Translead Elements / S. Liran, A. Marinov and N. Zeldes February 2001 New tables for the masses of translead elements have been calculated and submitted to ADNDT as a substitute and extension for these elements of the semiempirical shell-model mass equation (SSME) table presented in ADNDT 17(1976)431. We present two tables of calculated masses, for 351 nuclei with N from 94 to 126 and Z from 82 to 100, and for 1969 nuclei with N from 126 to 184 and Z from 82 to 126. The tables are calculated from a semiempirical shell-model mass equation based on Z=126 as a proton magic number which seems to be highly extrapolatable inside shell regions. Useful separation and decay energies are given as well. Some properties of the calculated masses and applications to superheavy elements are indicated in the introduction to the tables. The preprint of this work is available at the AMDC: http://csnwww.in2p3.fr/AMDC/theory/zel_adt2.pdf III - GENERAL INFORMATION Please send contributions to the next bulletin of the AMDC to: audi@csnsm.in2p3.fr General information on the AMDC are given in bulletin #01. AMDC Web: http://csnwww.in2p3.fr/amdc/ click:"access to files" or: http://csnwww.in2p3.fr/AMDC/ please, do not use any more ftp: the service has been discontinued "document.list" is the comprehensive list of documents and files available from AMDC. The AMDC bulletin is sent electronically 3 to 5 times per year. To subscribe / unsubscribe please send an email to: audi@csnsm.in2p3.fr Address: Atomic Mass Data Center C.S.N.S.M. (IN2P3-CNRS) Batiment 108 F-91405 Orsay campus (France) Telephone: +33 1 6915 5223 E-mail: audi@csnsm.in2p3.fr Telefax: +33 1 6915 5268 WWW: http://csnwww.in2p3.fr/AMDC/