Study of No isotopes with the GABRIELA array

Study of No isotopes with the GABRIELA array 127 th session of the Scientific Council

Separator for Heavy Elements Spectroscopy (SHELS) U-400 GABRIELA

Total working SET-UP in the world Dubna Gas Filled Separator (Russia) SHIP (Darmstadt, Germany) Berkeley Gas Filled Separator (USA) GARIS (Saitama, Japan) Gas-filled FPS Gas-filled SHELS/VASSILISSA (Dubna, Russia) FPS LIZE 3 (GANIL, France) RITU (JYFL, Finland) FMA (Argonne, USA) JAERI-RMS (Tokai, Japan) TASCA (Darmstadt, Germany) FPS Gas-filled FPS RDT Gas-filled RDT — Recoil Decay Tagging — Heavy element research FPS — Focal Plane Spectroscopy — Spectroscopy studies 3 RDT FPS

Region of interest Z > 100 106 Sg 101 Md 100 Fm 242 243 258 259 260 261 262 263 265 105 Db 256 257 258 259 260 261 262 263 104 Rf 253 254 255 256 257 258 259 260 261 262 263 103 Lr 252 253 254 255 256 257 258 259 260 261 262 250 251 252 253 254 255 256 257 258 259 260 102 No 248 245 247 248 249 250 251 252 253 254 255 256 257 258 259 260 246 247 248 249 250 251 252 253 254 255 256 257 258 259 244 246 245 266 262

GABRIELA Vacuum Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyser chamber. Detectors cooling before -30 C. It is used to registration the interest residues with subsequent α decays and fissions, as well as X-rays, γ-rays or conversion electrons. Set-up was upgrade at 2015 years and continues to improve.

Detectors Focal plane detector v. The active area of the strip detector is 100 x 100 mm 2: 128 x 128 strips 16384 pixels. v. Alpha particles registration efficiency is 70%. v. The energy resolution is 15 -20 ke. V for α-particles in the range of 5– 7 Me. V. Tunnel detector v It’s consisted of 8 Si-plats. v. The active area of the one strip detector is 50 x 60 mm 2: 32 x 32 strips – 1024 pixels, but all plats – 400 x 480 mm 2: 8192 pixels. v. Alpha particles registration efficiency is 70%. v. The energy resolution is 20 ke. V for αparticles in the range of 5– 7 Me. V.

Detectors Clover detector located behind a frontal DSSD. 4 Single crystal Ge-detectors surrounds tunnel DSSD. Efficiency of γ-rays registration was increased to 34% for γ-rays of 100 ke. V and 6% for 1000 ke. V. In future its value will be higher due to replace all single crystals detectors on clovers. Resolution energy is 2 ke. V.

Experiments 2019 № Experiment 1 48 Ca+208 Pb 2 48 Ca+206 Pb 252 No Collecting statistic. 3 48 Ca+204 Pb 250 No Study of isomers in 250 No. 4 22 Ne+238 U 256 No Study of isomers of 256 No. 6 48 Ca+208 Pb 254 No Study of 254 No isomers. Recoils 254 No, 252 No, 253 No Goals Study of 254 No isomers.

254 No → 254 No + 2 n � Cross section: 2μb � Flux ~ 8 • 1017 � 6 days � Beam energy: 226 Me. V � 48 Ca+208 Pb 254 No Isomers 51. 2 s 254 m 1 No 265 ms α 90% SF 0. 17% EC 10% α 0. 01 IT 100 SF 0. 02 254 m 2 No 184μs SF 0. 012 IT 100 Goal Study isomeric states and collecting more statistic of 254 No.

Recoil-fission(γ) correlation of 254 No T½ ~ 51. 2 s 254 m 1 No T ~ 265 ms ½ 254 m 2 No T ~ 184 μs ½ 252 No T ~ 2. 44 s ½ Recoil-fission(γ) correlation 245 chains 254 No has 152 events 252 No has 79 events Isomers of 14 events 1 event from 254 m 2 No has T½ ~ 2 ms that fits into the time range T½x 11. 13 events from 254 m 1 No has T½ ~ 309. 8 ms that fits into the time range T½x 2. Isomers In target 208 Pb. S (360μg) was impurity of 206 Pb. 254 No has branch on SF is 0. 17% and 252 No is 30%, that’s why these correlations good separated by lifetime.

Levels of 254 No 265 ms 8 7+ 6+ 778 940 856 5+ 4+ 887 3+ 10+ 8+ Correlated γ-rays spectrum of 254 No Good see gamma transition from isomeric level (265 ms) to excitation levels. Unfortunately, short lived event (2 ms) can not be attributed to the real events. 267 6+ 4+ 2+ 0+ 51. 2 s 159

Recoil-α(γ) correlation of 254 No and isomers. Time distribution for correlation Recoil-α in coincidence with γ-ray. Pic. 1 Pic. 2 Two calculates for different ranges of time and energy was made. Pic. 1 In calculate were used ranges of lifetime 1300 s and energy for 252 -254 No. Pic. 2 For isomers were used ranges of lifetime 28 s and energy of 9300 -9400 ke. V. Recoil-α(γ) correlation 119 events 254 No has 32 ev. , 253 No has 75 ev. , 252 No 12 ev. , isomers of 11 ev.

Alpha decay of No isotopes 8003, 8038, 8070, 7144, 8220, 8280 252 No 253 No 254 No 8372, 8415 2. 3 s more α 1. 7 m 8050, 8093 51. 2 s α α α 248 Fm 249 Fm 250 Fm 7800, 7830 36 s 7520 2. 6 m 7430 30 m Pic. 3 Pic. 4 Pic. 3 In reactions 48 Ca+208 Pb were received correlations 253 No-249 Fm and 252 No-248 Fm. Pic. 4 The same reactions was received Recoil-α correlation from 252, 253, 254 No. 252 and 253 nobelium is formed due to additive of 206, 207 Pb in target (208 Pb. S).

252 No → 252 No +2 n � Flux ~ 4. 6 • 1017 � Cross-section: 500 nb � SF = 22 000 and 4 days. � 48 Ca+206 Pb This reactions good known and is used for calibration by spontaneous fission. 20+ 18+ 484 16+ 453 14+ 12+ 375 10+ 8+ 6+ 4+ 2+ 0+ 224 167

250 No → 250 No + 2 n � Cross section: 13 nb � Flux: 2. 6 • 1018 � 13 days � 18000 events of SF � 48 Ca+204 Pb 250 No 4. 6 μs Isomer 250 m. No 46μs α? SF 100% IT 100 % Goal Find isomeric state and increase statistic of alpha decay of 250 No. The alpha decay estimate is small.

250 No T½ ~ 4, 6 μs 250 m. No T ~ 46 μs ½ 250 No In reaction 48 Ca+204 Pb were observed short lived events of 250 No with lifetime 26 μs and 250 m. No with 178μs. Lines 174 and 831 ke. V is correspond to them. Alpha decay wasn’t seen. Probability of α decay is 0. 000055%.

250 No 1050 6+ 174 4+ 876? 2+ 0+ 250 No have 0+(g. s), 250 m. No has 6+ level with energy 1050 ke. V. In experiment was observed gamma line 174, that can be transition 6+→ 4+.

Results � For 48 Ca(208 Pb, 2 n)254 No was collected good statistic. � Found: � 14 isomers in Recoil-fission correlations and � 11 isomers in Recoil-α correlations, � 52 chains of alpha decay from 253 No � 9 chains of alpha decay from 252 No. � For 48 Ca(206 Pb, 2 n)252 No was collected good statistic for calibration by SF. � For 48 Ca(204 Pb, 2 n)250 No was collected good statistic. Found: � short lived isomers in Recoil-fission correlations � new gamma transitions. � Alpha branch ~ 0. 000055%

Future ü New triplet of lenses: aperture length of 300 mm. ü 5 Ge-detectors, like Clover for GABRIELA. ü 4 Si-detectors 100 x 100 mm 2 for tunnel system. ü New target, diameter is 24 sm.

Peoples A. V. Yeremin, M. L. Chelnokov, V. I. Chepigin, A. V. Isaev, I. V. Izosimov, D. E. Katrasev, A. N. Kuznetsov, A. A. Kuznetsova, O. N. Malyshev, Yu. A. Popov, A. G. Popeko, E. A. Sokol, A. I. Svirikhin, K. Hauschild, A. Lopez-Martens O. Dorvaux, B. Gall, F. Dechery, H. Faure, Z. Asfari J. Piot , Ch. Stodel D. Tonev, E. Stefanova, P. Detistov B. Andel, P. Mosat S. Hofmann, J. Maurer, S. Heinz D. Pantelica, C. Nita, C. Borcea J. Gehlot