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A rotational band with five γ-ray transitions ranging from 2+ to 12+ states was identified in 40Ar. This band is linked through γ transitions from the excited 2+, 4+ and 6+ levels to the low-lying states; this determines the excitation energy and the spin–parity of the band. The deduced transition quadrupole moment of indicates that the band has a...
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... Predictions of superdeformed (SD) bands have been given based on different theoretical models around 40 Ca and in lighter alpha-like nuclei. Some of these suggestions have already been experimentally confirmed, SD candidate bands were experimentally found in this mass region in the 2000s such as in 28 Si [11], in 36 Ar [12], in 40 Ar [13], in 40 Ca [14] and in 44 Ti [15]. The SD character of a previously found band [16] was proved in 42 Ca [17]. ...
... A rotational band has been identified experimentally in 40 Ar by Ideguchi et al [13]. Based on the deduced quadrupole moment, the band has been identified as a SD one. ...
Superdeformed bands are determined from symmetry-considerations, and their in-band E2 transition strengths are predicted. Those light nuclei are studied which were investigated from the experimental side, and comparison can be made with observed data. The SU(3) symmetry seems to organize the experimental finding to a good approximation.
... SD bands were identified also in a few Ar isotopes, viz. 36 Ar [13], 38 Ar [14], and 40 Ar [15,16]. The origin of the observed SD band in 36 Ar was explained by the (s 1/2 d 3/2 ) 4 (p f ) 4 configuration [13]. ...
... Shell-model calculation shows that the band in 38 Ar was generated from 4p-6h excitations [14]. Similarly, for 40 Ar, the * abhijitbisoi@physics.iiests.ac.in origin of the SD band was explained by the mixing of different mp-mh (m = 0, 2, 4) configurations [15,16]. Therefore, this region gives a unique opportunity to investigate experimentally the interplay between single-particle and collective modes of excitations and interpret them theoretically by using microscopic large-basis shell-model calculations. ...
... However, at higher excitation energy, the signature of collective excitation has been found. 40 K is the isobaric partner nucleus of 40 Ar and 40 Ca where the existence of collectivity in terms of deformed and superdeformed bands has already been reported [11,15,16]. So, one may also expect collective excitations at higher excitation energy in 40 K, generated from multiparticle multihole excitations. ...
High spin states of 40K populated through the 27Al(19F,αnp)40K reaction at 68 MeV beam energy were studied using the Indian National Gamma Array (INGA) facility. Six new levels and fourteen new transitions were added to the existing level scheme. The spins and parities of most of the levels were assigned, modified, or confirmed from RDCO, RADO, and linear polarization measurements. The multipole mixing ratios (δ) for most of the transitions were measured. Large-basis shell-model calculations were performed to understand the microscopic origin of the levels. Different particle restrictions in sd and pf shell orbitals were used to explain the experimental results.
... Such states, associated with magic shells N = Z = 20, have been found in 36.40 Ar, 40.42 Ca, and 44 Ti nuclei [11][12][13][14][15]. ...
Energy spectra to the ground state and excited states of 46 Ti have been measured for the 45 Sc(3 He, d) 46 Ti reaction at a bombarding energy of 29 MeV. Excited levels of 46 Ti were observed in a wide energy range from 2 to 16.5 MeV. Levels from 10.4 to 16.5 MeV are observed for the first time and populated with a high probability. The population of high-lying states with energies E x ≥ 10 MeV in 46 Ti and their structure can be explained as the lowest excited levels of the 42 Ca + 4 He alpha-cluster system corresponding to the superdeformed state of 46 Ti.
... Experimental evidence [776][777][778][779][780] for SC and particle-hole excitations has been found in [36][37][38][39][40] , corroborated by shell-model [778,780], cranked Nilsson-Strutinsky [780], and cranked HFB [777] calculations. SC in 36 Ar 18 has also been considered [169] within RMF theory, in conjunction with the hypernucleus 37 Λ Ar. ...
... Experimental evidence [776][777][778][779][780] for SC and particle-hole excitations has been found in [36][37][38][39][40] , corroborated by shell-model [778,780], cranked Nilsson-Strutinsky [780], and cranked HFB [777] calculations. SC in 36 Ar 18 has also been considered [169] within RMF theory, in conjunction with the hypernucleus 37 Λ Ar. ...
The last decade has seen a rapid growth in our understanding of the microscopic origins of shape coexistence, assisted by the new data provided by the modern radioactive ion beam facilities built worldwide. Islands of the nuclear chart in which shape coexistence can occur have been identified, and the different microscopic particle–hole excitation mechanisms leading to neutron-induced or proton-induced shape coexistence have been clarified. The relation of shape coexistence to the islands of inversion, appearing in light nuclei, to the new spin-aligned phase appearing in N=Z nuclei, as well as to shape/phase transitions occurring in medium mass and heavy nuclei, has been understood. In the present review, these developments are considered within the shell-model and mean-field approaches, as well as by symmetry methods. In addition, based on systematics of data, as well as on symmetry considerations, quantitative rules are developed, predicting regions in which shape coexistence can appear, as a possible guide for further experimental efforts that can help in improving our understanding of the details of the nucleon–nucleon interaction, as well as of its modifications occurring far from stability.
... In summary, much experimental and theoretical evidence for SC is accumulated for 36 Experimental evidence [236,355,718,720,730] for SC and particle-hole excitations has been found in [36][37][38][39][40] , corroborated by shell model [718,730], cranked Nilsson-Strutinsky [730] and cranked HFB [355] calculations. SC in 36 Ar 18 has also been considered [797] within relativistic mean field theory, in conjunction with the hypernucleus 37 Λ Ar. ...
... In summary, much experimental and theoretical evidence for SC is accumulated for 36 Experimental evidence [236,355,718,720,730] for SC and particle-hole excitations has been found in [36][37][38][39][40] , corroborated by shell model [718,730], cranked Nilsson-Strutinsky [730] and cranked HFB [355] calculations. SC in 36 Ar 18 has also been considered [797] within relativistic mean field theory, in conjunction with the hypernucleus 37 Λ Ar. ...
The last decade has seen a rapid growth of our understanding of the microscopic origins of shape coexistence, assisted by the new data provided by the modern radioactive ion beam facilities built worldwide. Islands of the nuclear chart in which shape coexistence can occur have been identified, and the different microscopic particle-hole excitation mechanisms leading to neutron-induced or proton-induced shape coexistence have been clarified. The relation of shape coexistence to the islands of inversion, appearing in light nuclei, to the new spin-aligned phase appearing in N=Z nuclei, as well as to shape/phase transitions occurring in medium mass and heavy nuclei, has been understood. In the present review, these developments are considered within the shell model and mean field approaches, as well as by symmetry methods. In addition, based on systematics of data, as well as on symmetry considerations, quantitative rules are developed, predicting regions in which shape coexistence can appear, as a possible guide for further experimental efforts, which can help in improving our understanding of the details of the nucleon-nucleon interaction, as well as of its modifications occurring far from stability.
... A different trend is seen for the 0 + 2 state, which generally represents a different shape of the nucleus from the ground state. For 40 Ar, the 0 + 2 state is described to be part of a super-deformed band in Ref. [47]. With increasing neutron number, the energy of this state is found to increase, attaining a maximum value for 44 Ar. ...
Results from the study of $\beta^-$-decay of $^{45}$Cl, produced in the fragmentation of a 140-MeV/u $^{48}$Ca beam, are presented. The half-life for $^{45}$Cl $\beta$-decay is measured to be 513(36) ms. The $\beta^-$ and $\beta^- 1n$ decay of $^{45}$Cl populated excited states in $^{45,44}$Ar, respectively. On the basis of $\gamma$-ray singles and $\gamma$-$\gamma$ coincidence data, decay schemes for the two daughter nuclei have been established. They are compared with shell model calculations using the FSU interaction. The low-lying negative parity states for $^{45}$Ar are well described by a single particle (neutron) occupying orbitals near the Fermi surface, whereas neutron excitations across the $N = 20$ shell gap are needed to explain the positive-parity states which are expected to be populated in allowed Gamow-Teller $\beta$-decay of $^{45}$Cl. The highest $\beta$-feeding to the 5/2$^+$ state in $^{45}$Ar from the ground state of $^{45}$Cl points towards a 3/2$^+$ spin-parity assignment of the ground state of the parent over the other possibility of 1/2$^+$. The high Q$_{\beta^-}$ value of $^{45}$Cl decay allows for the population of $1p1h$ states above the neutron separation energy in $^{45}$Ar leading to positive parity states of $^{44}$Ar being populated by removal of one neutron from the $sd$ shell. The spin-parities of the excited levels in $^{44}$Ar are tentatively assigned for the first time by comparison with the shell model calculations. The 2978~keV level of $^{44}$Ar is identified as the excited 0$^+$ level which could correspond to a different configuration from the ground state.
... Furthermore, there is another unique feature of the SD band in 40 Ca. Although SD nuclei are reported in several mass regions [21], SD band heads with J π ¼ 0 þ are only observed in the A ¼ 40 [22,23] and fission-isomer [21] regions. This makes it difficult to study their properties, such as mixing with less-deformed configurations, in detail. ...
The electric monopole (E0) transition strength ρ^{2} for the transition connecting the third 0^{+} level, a "superdeformed" band head, to the "spherical" 0^{+} ground state in doubly magic ^{40}Ca is determined via e^{+}e^{-} pair-conversion spectroscopy. The measured value ρ^{2}(E0;0_{3}^{+}→0_{1}^{+})=2.3(5)×10^{-3} is the smallest ρ^{2}(E0;0^{+}→0^{+}) found in A<50 nuclei. In contrast, the E0 transition strength to the ground state observed from the second 0^{+} state, a band head of "normal" deformation, is an order of magnitude larger ρ^{2}(E0;0_{2}^{+}→0_{1}^{+})=25.9(16)×10^{-3}, which shows significant mixing between these two states. Large-scale shell-model (LSSM) calculations are performed to understand the microscopic structure of the excited states and the configuration mixing between them; experimental ρ^{2} values in ^{40}Ca and neighboring isotopes are well reproduced by the LSSM calculations. The unusually small ρ^{2}(E0;0_{3}^{+}→0_{1}^{+}) value is due to destructive interference in the mixing of shape-coexisting structures, which are based on several different multiparticle-multihole excitations. This observation goes beyond the usual treatment of E0 strengths, where two-state shape mixing cannot result in destructive interference.
... In addition to the pn correlation, interesting phenomena, such as emergence of superdeformed (SD) bands [13][14][15], clusterization in nuclei [16,17] can be studied in sd-shell nuclei. To describe the high-spin states in this region, cross-shell excitations from the sd to the f p shells have to be taken into account. ...
... To describe the high-spin states in this region, cross-shell excitations from the sd to the f p shells have to be taken into account. The emergence of SD bands in 36 Ar [13], 40 Ar [14], and 40 Ca [15] is attributed to the multiparticle multihole excitations. The low-spin structure has been reproduced well by shell-model calculations with, such as the universal sd (USD) interaction [18]. ...
Excited states in S35 were investigated by in-beam γ-ray spectroscopy using the Mg26(O18,2α1n) fusion-evaporation reaction. The deexciting γ rays were measured with germanium detector arrays along with the measurement of evaporated charged particles in a 4π-segmented Si detector array. The level scheme was extended up to 12.47 MeV. The obtained level structure is compared with the large-scale shell-model calculations. The possibility of isoscalar-pair excited states is discussed for J=(17/2) states with comparison between the experimental and theoretical results.
... The study of SD bands has been an active field in nuclear physics, and the rotational bands have been observed up to high spins in various mass regions [3] since their discovery in 1986 [4]. Recently, the high-spin structures in light N Z nuclei near the doubly magic 40 Ca nucleus have been studied experimentally [5][6][7][8][9][10][11][12][13][14][15][16], and SD bands have been observed in PTEP 2020, 063D02 S. Sakai et al. ...
... nuclei such as 36 Ar [5,6], 40 Ar [9], 40 Ca [11,12], 42 Ca [17], and 44 Ti [16]. An interesting feature in this mass region is the coexistence of states with different shapes at low energy, which is caused by single-particle excitations from the core and the coherent shell effects of neutrons and protons. ...
We investigate the possible occurrence of highly elongated shapes near the yrast line in $^{40}$Ca and $^{41}$Ca at high spins on the basis of the nuclear energy-density functional method. Both the superdeformed (SD) yrast configuration and the yrare configurations on top of the SD band are described by solving the cranked Skyme–Kohn–Sham equation in the three-dimensional coordinate space representation. It is suggested that some of the excited SD bands undergo band crossings and develop to hyperdeformation (HD) beyond $J \simeq 25 \hbar$ in $^{40}$Ca. We find that the change of triaxiality in response to rotation plays a decisive role in the shape evolution towards HD, and that this is governed by the signature quantum number of the last occupied orbital at low spins. This mechanism can be verified in an experimental observation of the positive-parity SD yrast signature-partner bands in $^{41}$Ca, one of which ($\alpha=+1/2$) undergoes crossings with the HD band, while the other ($\alpha=-1/2$) shows smooth evolution from collective rotation at low spins to non-collective rotation with an oblate shape at termination.
... The study of SD bands has been an active field in nuclear physics, and the rotational bands have been observed up to high spins in various mass regions [3] since their discovery in 1986 [4]. Recently, the high-spin structures in light N Z nuclei near the doubly magic 40 Ca nucleus have been studied experimentally [5][6][7][8][9][10][11][12][13][14][15][16], and SD bands have been observed in PTEP 2020, 063D02 S. Sakai et al. nuclei such as 36 Ar [5,6], 40 Ar [9], 40 Ca [11,12], 42 Ca [17], and 44 Ti [16]. An interesting feature in this mass region is the coexistence of states with different shapes at low energy, which is caused by single-particle excitations from the core and the coherent shell effects of neutrons and protons. ...
... The study of SD bands has been an active field in nuclear physics, and the rotational bands have been observed up to high spins in various mass regions [3] since their discovery in 1986 [4]. Recently, the high-spin structures in light N Z nuclei near the doubly magic 40 Ca nucleus have been studied experimentally [5][6][7][8][9][10][11][12][13][14][15][16], and SD bands have been observed in PTEP 2020, 063D02 S. Sakai et al. nuclei such as 36 Ar [5,6], 40 Ar [9], 40 Ca [11,12], 42 Ca [17], and 44 Ti [16]. An interesting feature in this mass region is the coexistence of states with different shapes at low energy, which is caused by single-particle excitations from the core and the coherent shell effects of neutrons and protons. ...
We investigate the possible occurrence of the highly-elongated shapes near the yrast line in $^{40}$Ca and $^{41}$Ca at high spins on the basis of the nuclear energy-density functional method. Not only the superdeformed (SD) yrast configuration but the yrare configurations on top of the SD band are described by solving the cranked Skyme-Kohn-Sham equation in the three-dimensional coordinate-space representation. It is suggested that some of the excited SD bands undergo band crossings and develop to the hyperdeformation (HD) beyond $J \simeq 25 \hbar$ in $^{40}$Ca. We find that the change of triaxiality in response to rotation plays a decisive role for the shape evolution towards HD, and that this is governed by the signature quantum number of the last occupied orbital at low spins. This mechanism can be verified in an experimental observation of the positive-parity SD yrast signature-partner bands in $^{41}$Ca, one of which ($\alpha=+1/2$) undergoes crossings with the HD band while the other ($\alpha=-1/2$) shows the smooth evolution from the collective rotation at low spins to the non-collective rotation with oblate shape at the termination.
