In the last years we carried out several experiments aimed to investigate properties of short-lived SF isotopes. The neutron-deficient isotopes of nobelium were produced in fusion-evaporation ...reactions using206,208Pb targets and an intense48Ca-beam. Fusion-evaporation residues were separated by the SHELS separator and implanted into a large-area double-sided (48 × 48) strip silicon detector surrounded by3He-based neutron counters. Half-lives and decay branching ratios for252,254No isotopes were measured. The average number of neutrons per spontaneous fission of254No determined for the first time.
Properties of the radioactive decay of No, Rf isotopes are studied in the reaction
50
Ti +
209
Bi →
259
Db* . The cross sections of Db and Rf isotopes production in channels
xn
and
pxn
, ...respectively, are measured. High intensity beams of accelerated heavy ions
22
Ne,
48
Ca,
50
Ti, and
54
Cr of the U400 cyclotron and SHELS kinematic separator are used in the experiments.
The experiments of detailed study of No and Rf isotopes radioactive decay properties in complete fusion reactions50Ti+208Pb and48Ca+208,206,204Pb with subsequent neutron evaporation from the excited ...compound nucleus at the kinematic separator SHELS were performed in FLNR JINR. The data of the256Rf decay properties and preliminary data of250No decay properties are presented.
The analysis of fission events following the implantation of evaporation residues produced in the fusion reaction of 50Ti and 209Bi at different bombarding energies has revealed 5 millisecond decays, ...which are attributed to the spontaneous fission of proton-evaporation channels. The average cross sections for proton evaporation are found to be ∼100 and 10 times smaller than the largest neutron-evaporation channel cross section at the same excitation energy. These results suggest that the proton evaporation channel, albeit weak, may represent a realistic alternative to synthesize new, more neutron rich super heavy nuclei.
The physical limitations of the amount of data stored on optical media are pushing researchers to create new materials and methods for recording and reading data. One of the promising areas is the ...use of fluorescent compounds. Within the framework of this work, polymer structures of optical fluorescent memory with a recording medium based on 3-(thiophene-2-carbonyl) -2- (furan-2-yl) -4n-chromen-4-one in polymethylmethacrylate have been fabricated and investigated. The concentration of chromone was 5% (wt.), Which during recording made it possible to achieve optical density values at λ = 442 nm in the range of 0.01 - 0.02 with a central layer thickness of 1-3 µm. In the structures developed, the process of two-photon information recording and fluorescent parallel reading is realized. The threshold recording power density for providing a two-photon process was (5.1 ± 0.4) 105 W/cm2.
Experiments aimed at synthesizing and investigating the features of radioactive decay of isotopes of superheavy elements (
Z
≥ 110) have been conducted in the Flerov Laboratory of Nuclear Reactions ...at the Joint Institute for Nuclear Research. Complete fusion reactions of an accelerated beam of
48
Ca ions with transactinide targets with the subsequent evaporation of several neutrons from excited compound nucleus are typically used in these experiments. “Exotic” reaction channels with the evaporation of protons and several neutrons may be used to produce more neutron-rich isotopes of superheavy elements. The production cross sections were measured in experiments at the SHELS separator for Db and Rf isotopes produced in
xn
and
pxn
channels of the
50
Ti +
209
Bi →
259
Db* reaction. The ratio of cross sections σ(
xn
)/σ(
pxn
) was on the order of 100.
Fission hindrances in transfermium nuclei Lopez-Martens, A.; Hauschild, K.; Svirikhin, A.I. ...
EPJ Web of Conferences,
2023, Letnik:
290
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Very heavy nuclei owe their stability against spontaneous fission to quantum shell effects, which depend on the local density of single-particle states. The height but also the width and the ...structure of the barrier in multi-dimensional deformation space determine the fission half-lives. Other effects come into play, such as the conservation of quantum numbers and superfluidity or stiffness of the system in the fission process. This is why odd nuclei have longer fission partial half-lives with respect to their even neighbours and also why multi-quasi-particle states, such as high-K states, are thought to be more stable against fission than the ground state. We will report here on two different fission studies carried out with the GABRIELA detector array at the focal plane of the recoil separator SHELS. The first study concerns the fission properties of
253
Rf, the most neutron deficient Rf isotope known to date. The second study focusses on a new measurement of the fission hindrance of the known 8
-
isomer in
254
No.
The New 249No Isotope Svirikhin, A. I.; Yeremin, A. V.; Zamyatin, N. I. ...
Physics of particles and nuclei letters,
2021/7, Letnik:
18, Številka:
4
Journal Article
Recenzirano
In the reaction of complete fusion of
48
Ca-ions with a
204
Pb target, a new α line, related to the decay of a new, previously unknown isotope (
249
No), has been detected in an experiment carried ...out at the SHELS separator. The α decay energy (
E
α
= 9129 keV) and the half-life (
T
1/2
= 38.1 ± 2.5 ms) are measured using the GABRIELA detector array. The SF branching ratio was estimated (
b
SF
≤ 0.2%).
Spontaneous fissions of the
252
No and
254
No nobelium isotopes have been studied in a series of experiments with the SHELS separator. These isotopes are produced by colliding a beam of
48
Ca ions ...from the U-400 cyclotron with the
206
Pb and
208
Pb targets. The measured characteristics of the
252
No and
254
No spontaneous fissions include their half-lives, total kinetic energies of fission fragments, and prompt-neutron multiplicities. The average number of neutrons per
254
No spontaneous-fission act is measured for the first time as 4.88 ± 0.53.
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