- Huang, T;
- Seweryniak, D;
- Back, BB;
- Bender, PC;
- Carpenter, MP;
- Chowdhury, P;
- Clark, RM;
- Copp, PA;
- He, X-T;
- Herzberg, RD;
- Hoff, DEM;
- Jayatissa, H;
- Khoo, TL;
- Kondev, FG;
- Morgan, G;
- Morse, C;
- Korichi, A;
- Lauritsen, T;
- Müller-Gatermann, C;
- Potterveld, DH;
- Reviol, W;
- Rogers, AM;
- Saha, S;
- Savard, G;
- Sharma, K;
- Stolze, S;
- Waniganeththi, S;
- Wilson, GL;
- Wu, J;
- Xu, Y-F;
- Zhu, S
The products of the Tl203,205(Ti50,2n) fusion-evaporation reactions were studied using the recently commissioned Argonne Gas-Filled Analyzer at Argonne National Laboratory. Two α-decay activities with energies of 9210(19) and 9246(19) keV and half-lives of 42-14+42 and 24.4-4.5+7.0 ms were observed which were followed by the known α decays of Md247 and Es243. They are interpreted as originating from the 1/2-[521] and 7/2-[514] single-proton Nilsson states in the hitherto unknown isotope Lr251. From the measured Qα values the 1/2- level was placed 117(27) keV above the 7/2- level in Lr251 in contrast to Lr255 where the 1/2- level is the lowest. Also, the α decay of Lr253 was studied in more detail and a new α line at 8660(20) keV was found and a new half-life value of 2.46(32) s for an isomeric state in Lr253 was measured. The Lr251,253,255Qα values were compared with predictions of various mass models. The relative energies of the 1/2-[521] and 7/2-[514] single-proton Nilsson states in Lr251,253,255 isotopes were compared with results of the cranking shell model with pairing treated using the particle-number-conserving method. The level separation and, in particular, the level order change between Lr251 and Lr255 was reproduced only when the hexacontetrapole deformation 6 was included in the calculations.