D. Kocheva
A5024453872- Nuclear physics research studies
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Quantum Chromodynamics and Particle Interactions
- Astronomical and nuclear sciences
- Advanced Chemical Physics Studies
- Advanced NMR Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Nuclear reactor physics and engineering
- Particle physics theoretical and experimental studies
- Atomic and Subatomic Physics Research
- Rare-earth and actinide compounds
- Radiation Detection and Scintillator Technologies
- Neutrino Physics Research
- Astronomical Observations and Instrumentation
- Particle Detector Development and Performance
- Magnetic Properties of Alloys
Sofia University "St. Kliment Ohridski"
2016-2024
Institut National de Physique Nucléaire et de Physique des Particules
2019
Université Paris-Sud
2019
Centre National de la Recherche Scientifique
2019
Université Paris-Saclay
2019
Low-lying states in $^{206}\mathrm{Po}$ were investigated using the fast-timing technique with ${\mathrm{LaBr}}_{3}(\mathrm{Ce})$ and high-purity germanium detectors. The excited this nucleus populated via two consecutive electron capture decays from $^{206}\mathrm{Rn}$. parent isotope was produced $^{194}\mathrm{Pt}(^{16}\mathrm{O},4n)^{206}\mathrm{Rn}$ fusion-evaporation reaction at FN-Tandem facility Institute for Nuclear Physics, University of Cologne. previously known value lifetime...
We present the results from an experiment dedicated to search for quadrupole-collective isovector valence-shell excitations, states with so-called mixed proton-neutron symmetry (MSS), of $^{212}\mathrm{Po}$. This nucleus was studied in $\ensuremath{\alpha}\text{-transfer}$ reaction. The lifetimes two short-lived excited states, candidates one-phonon MSS, were determined by utilizing Doppler shift attenuation method. experimental are qualitative agreement a simple $\text{single-}j$ shell...
The lifetime of the ${2}_{1}^{+}$ state $^{212}\mathrm{Po}$ was measured in $^{208}\mathrm{Pb}$($^{12}\mathrm{C},^{8}\mathrm{Be}$)$^{212}\mathrm{Po}$ transfer reaction by $\ensuremath{\gamma}$-ray spectroscopy employing recoil distance Doppler shift (RDDS) method. derived absolute $B(E2)$ value 2.6(3) W.u. indicates a low collectivity and contradicts previous claims $\ensuremath{\alpha}$-cluster components structure state. It is demonstrated that consistent description properties...
Low-lying yrast states of $^{204}\mathrm{Po}$ and $^{206}\mathrm{Po}$ were investigated by the $\ensuremath{\gamma}--\ensuremath{\gamma}$ fast timing technique with ${\mathrm{LaBr}}_{3}$(Ce) detectors. Excited these nuclei populated in $^{197}\mathrm{Au}(^{11}\mathrm{B},4n)^{204}\mathrm{Po}$ $^{198}\mathrm{Pt}(^{12}\mathrm{C},4n)^{206}\mathrm{Po}$ fusion-evaporation reactions, respectively. The beams delivered FN-Tandem accelerator at University Cologne. lifetimes ${4}_{1}^{+}$ both...
The $5/{2}_{1}^{\ensuremath{-}}$, $9/{2}_{1}^{\ensuremath{-}}$, and $11/{2}_{1}^{\ensuremath{-}}$ states in $^{209}\mathrm{Po}$ were populated the $\ensuremath{\beta}$ decay of $^{209}\mathrm{At}$ their lifetimes measured using electronic $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ fast timing technique. lifetime $9/{2}_{1}^{\ensuremath{-}}$ state is for first time. $5/{2}_{1}^{\ensuremath{-}}$ to be shorter than value adopted literature while agrees well with previous...
A lifetime measurement of the 19/2− state in 207Pb has been performed using Recoil Distance Doppler-Shift (RDDS) method. The nuclei interest were produced multi-nucleon transfer reactions induced by a 208Pb beam impinging on 100Mo enriched target. beam-like detected and identified terms their atomic mass number VAMOS++ spectrometer while prompt γ rays AGATA tracking array. measured large reduced transition probability B(E3,19/2−→13/2+)=40(8) W.u. is first indication octupole phonon at high...
Half-lives of the low-lying yrast states 212Po have been measured using delayed coincidence fast-timing method. We report on first measurement 41+ half-life, as well a new 61+ half-life with improved accuracy compared to previous studies. The extracted lifetime and state determined be 100(14) ps 1.66(28) ns respectively. With these measurements, precise values are now available for reduced transition strengths B(E2) all ground band levels in up 8+ state, particular B(E2; 41+→21+) = 9.4(13)...
The lifetimes of the first excited ${4}^{+}$ and ${6}^{+}$ states in $^{212}\mathrm{Po}$ were measured using recoil-distance Doppler shift method. nucleus interest was populated $^{208}\mathrm{Pb}(^{18}\mathrm{O},^{14}\mathrm{C})^{212}\mathrm{Po}$ reaction. experimental results are compared to large-scale shell model calculations performed recently developed H208 effective interaction. describe well low-lying structure with an exception ${2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+}$...
The nucleus $^{100}\mathrm{Ru}$ appears to be a good candidate for the E(5) critical point symmetry which describes U(5)-SO(6) shape phase transition. To investigate this with respect electromagnetic transition strengths, lifetime measurements of its yrast states have been performed using recoil distance Doppler shift technique as well attenuation method. As result, lifetimes ${2}^{+}$, ${4}^{+}$, and ${8}^{+}$ were determined. deduced strengths are compared predictions results excited...
The lifetimes of the 21+ and 41+ states Po208 were measured in α-transfer reaction Pb204(C12,Be8)Po208 by γ-ray spectroscopy utilizing recoil distance Doppler shift method. newly extracted transition strengths alongside ones decay 22+ state compared to results large-scale shell-model calculations using an effective interaction derived from realistic CD-Bonn nucleon-nucleon potential. comparison indicates importance quadrupole isovector excitations valence shell for a fine tuning two-body...
A $\ensuremath{\gamma}$-ray spectroscopic study of $^{212}\mathrm{Po}$ was performed at the Grand Acc\'el\'erateur National d'Ions Lourds, using inverse kinematics $\ensuremath{\alpha}$-transfer reaction $^{12}\mathrm{C}(^{208}\mathrm{Pb},^{212}\mathrm{Po})^{8}\mathrm{Be}$ and AGATA spectrometer. careful analysis based on $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence relations allowed us to establish 14 new excited states in energy range between 1.9 3.3 MeV. None these states,...
Abstract The nucleus 206 Po was studied in the two proton transfer reaction 204 Pb( 16 O, 14 C) and lifetime of first excited 2 + state determined by utilizing Recoil Distance Doppler Shift method. experimental results are compared with shell-model calculations based on different effective interactions. qualitatively reproduced experimentally observed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>B</mml:mi> <mml:mo stretchy="false">(</mml:mo>...
Abstract The half-life of the first 6 + state in 136 Ce has been measured as T 1/2 = 41(12) ps using γ -ray fast-timing technique with ν -ball spectrometer at ALTO Tandem Accelerator, Orsay, France. states interest have populated via 128 Te( 12 C,4n ) fusion-evaporation reaction. A comparison is made between value obtained for reduced transition probability <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>B</mml:mi> <mml:mo stretchy="false">(</mml:mo>...
In this work we present the results from two experiments dedicated to search for quadrupolecollective isovector valence-shell excitation, states with so-called mixed proton-neutron symmetry (MSS), in nuclei around doubly magic nucleus 208Pb. 212Po was studied an α-transfer reaction. 204Hg inverse kinematics Coulomb excitation reaction on a carbon target. Both provide indications existence of one-phonon MSSs. Those are first experimentally identified MSSs mass A ≈ 208 region.
The multi-nucleon transfer reaction mechanism was used to produce and study nuclei in the vicinity of 208Pb. This mass region is a test case for nuclear shell model. identification fragments performed with large acceptance magnetic spectrometer VAMOS++ coupled AGATA γ-tracking array. experiment aimed determine both lifetimes gyromagnetic ratios excited states Cologne plunger device. analysis indicates promising results possibility several new this region.
Projectile Coulomb excitation experiments were performed at HIE-ISOLDE CERN with the radioactive ion beams of 140 Nd and 142 Sm. Ions an energy 4:62 MeV/A impinging on a 1.45 mg/cm 2 thick 208 Pb target. The γ-rays depopulating Coulomb-excited states recorded by HPGe-array MINIBALL scattered particles detected double-sided silicon strip detector. Experimental intensities used for determination electromagnetic transition matrix elements. A preliminary result B(M1; + 3 → 1 ) upper limit case...
Low-lying yrast states in 204 Po and 206 have been investigated by the γ-γ fast timing technique with LaBr 3 (Ce) detectors. Excited of these nuclei were populated 197 Au( 11 B,4n) 198 Pt( 12 C,4n) fusion-evaporation reactions, respectively, at FN-Tandem Facility University Cologne. The lifetimes 4 + 1 both measured, along an upper limit for 2 state Po. preliminary results are discussed scope systematic behavior transition strengths between polonium isotopes.
Abstract In this study we present the preliminary results about lifetimes of <?CDATA ${2}_{2}^{+}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mn>2</mml:mn> <mml:mo>+</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> , ${4}_{1}^{+}$?> <mml:mn>4</mml:mn> <mml:mn>1</mml:mn> states 208 Po and upper limit lifetime ${2}_{1}^{+}$?> state. For measuring Recoil Distance Doppler Shift (RDDS) method for state Attenuation (DSAM) were used....
The lifetime of the state in 208Po has been measured using γ − fast-timing technique with LaBr3(Ce) Detectors. experiment was performed at FN Tandem facility University Cologne. preliminary results are discussed scope systematic behavior transition strengths between yrast states polonium isotopes.
A projectile Coulomb-excitation experiment was performed at the radioactive-ion beam facility HIE-ISOLDE CERN to obtain E2 and M1 transition matrix elements of Nd140 using multistep code gosia. The absolute strengths, B(M1;22+→21+)=0.033(8)μN2,B(M1;23+→21+)=0.26−0.10+0.11μN2, B(M1;24+→21+)<0.04μN2, identify 23+ state as main fragment one-quadrupole-phonon proton-neutron mixed-symmetry Nd140. degree F-spin mixing in quantified with determination element VF−mix<7−7+13keV.Received 7 August...