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We study effects of higher-order antinematic interactions on the critical behavior of the antiferromagnetic (AFM) $XY$ model on a triangular lattice, using Monte Carlo simulations. The parameter $q$ of the generalized antinematic (ANq) interaction is found to have a pronounced effect on the phase diagram topology by inducing new quasi-long-range ordered phases due to competition with the conventional AFM interaction as well as geometrical frustration. For values of $q$ divisible by 3 the conflict between the two interactions results in a frustrated canted AFM phase appearing at low temperatures wedged between the AFM and ANq phases. For $q$ nondivisible by 3 with the increase of $q$ one can observe the evolution of the phase diagram topology featuring two ($q=2$), three ($q=4,5$) and four ($q \geq 7$) ordered phases. In addition to the two phases previously found for $q=2$, the first new phase with solely AFM ordering arises for $q=4$ in the limit of strong AFM coupling and higher temperatures by separating from the phase with the coexisting AFM and ANq orderings. For $q=7$ another phase with AFM ordering but multimodal spin distribution in each sublattice appears at intermediate temperatures. All these algebraic phases also display standard and generalized chiral long-range orderings, which decouple at higher temperatures in the regime of dominant ANq (AFM) interaction for $q \geq 4$ ($q \geq 7$) preserving only the generalized (standard) chiral ordering., Comment: 23 pages, 10 figures

Critical properties of a geometrically frustrated generalized $XY$ model with antiferromagnetic (AFM) and third-order antinematic (AN3) couplings on a triangular lattice are studied by Monte Carlo simulation. It is found that such a generalization leads to a phase diagram consisting of three different quasi-long-range ordered (QLRO) phases. Compared to the model with the second-order antinematic (AN2) coupling, besides the AFM and AN3 phases which appear in the limits of relatively strong AFM and AN3 interactions, respectively, it includes an additional complex canted antiferromagnetic (CAFM) phase. It emerges at lower temperatures, wedged between the AFM and AN3 phases, as a result of the competition between the AFM and AN3 couplings, which is absent in the model with the AN2 coupling. The AFM-CAFM and AN3-CAFM phase transitions are concluded to belong to the weak Ising and weak three-state Potts universality classes, respectively. Additionally, all three QLRO phases also feature true LRO of the standard and generalized chiralities, which both vanish simultaneously at second-order phase transitions with non-Ising critical exponents and the critical temperatures slightly higher than the magnetic and nematic order-disorder transition temperatures., Comment: 20 pages, 8 figures

High-spin states of the $^{44}$Sc nucleus, populated in the 68 MeV $^{18}$O + $^{30}$Si reaction, have been studied in a $\gamma-\gamma$-recoil coincidence experiment. The detailed decay pattern, with various paths and cross-transitions, has been extended up to 9.1 MeV. High-quality DCO and polarization information assign spins and parities for the majority of the observed levels. The negative-parity states are discussed and compared with rotational bands in neighbouring $f_{7/2}$-shell nuclei.

High-spin states in 45Sc, 45Ti and 43Ca were studied by means of multiple γ- and γ-recoil-coincidences with the use of the GASP array and the Recoil Mass Spectrometer. The nuclei were populated in the 60 MeV 18O +30Si reaction. For the DSAM lifetime measurement the 35Cl +12C reversed kinematics reaction was used. In the article, a complete description of the experimental techniques used in course of the performed experiments is presented. The level schemes and the detailed information on the observed state properties, including B(M1) and B(E2) transition rates are inserted as well as their shell model interpretation.

High spin states in nuclei around 208Pb were populated in deep inelastic collisions of 76Ge, 136Xe, and 208Pb projectiles with 208Pb targets at beam energies about 12% above the Coulomb barrier. New states in 209Pb were found by measuring γ-γ-coincidences. They are interpreted as the yrast states that originate from the coupling of one neutron to the lowest excitations of the 208Pb core. The results are discussed in the frame of the shell model.

The high-spin states in 45 Sc were studied with the GASP multidetector array. The nuclei were excited by the 30 Si( 18 O,p2n) 45 Sc reaction at E LAB =60 MeV and separated with the Recoil Mass Spectrometer. Several new high-spin levels extending the known single-particle and collective structures were observed. Energies of the negative-parity states agree with the shell model predictions whereas the positive-parity-intruder rotational band extends up to very high rotational frequencies and continues beyond the maximum angular momentum available from the single-particle f 7 2 configuration.

High-spin states of the 42Ca nucleus, populated in the 68 MeV 18O + 30Si reaction, have been studied in a γ-γ-recoil coincidence experiment. The level scheme of 42Ca has been extended up to 13.7 MeV. An elaborate decay pattern with various paths, together with high-quality DCO and polarization information assigns spins and parities for almost all observed levels. The sequence of non-yrast positive-parity states is discussed and compared with highly deformed bands in 36Ar and 40Ca.

Excited states in198,199Po have been studied by in-beamγ-ray spectroscopy. These nuclei were produced in the 4n and 5n reaction channels for 115 MeV20Ne on183W-targets. Multipolarities and mixing ratios ofγ-transitions were determined from DCO-ratios, leading to spin/parity assignments. In198Po,γ-cascades have been observed above several excited levels that are similar to the vibration-like structure built on the ground state. In199Po, the coupling of the oddi13/2 neutron seems to favor the spherical shape of the even core; no levels resembling the intruder states of the even nuclei are found. A semi-quantitative evaluation of the cross-sections for nuclei produced in fission and multi-particle transfer is presented.

In a [gamma][gamma]-coincidence study of collisions of [sup 106]Cd with 247 MeV [sup 54]Fe we have quantitatively identified the product nuclei formed in fusion-evaporation as well as in binary reactions. Individual binary processes were sampled through identification of numerous exit partner pairs with the help of [gamma][gamma] cross coincidences. The data also provide information on the angular momentum transferred to the product nuclei and on charge equilibration in the collision process. The results reveal important features of heavy-ion collisions that are difficult to obtain in measurements using charged particle detection alone.

The feasibility of measuring g -factors using the TDPAD method applied to high-energy, heavy fragmentation products is explored. The 2623keV $\ensuremath I^{\pi}=12^+$ isomer in 192Pb with $ \tau$ = 1.57 μs has been produced using the fragmentation of a 1A GeV 238U beam. The results presented demonstrate for the first time that such heavy nuclei produced in a fragmentation reaction with a relativistic beam are sufficiently well spin-aligned. Moreover, the rather large value of the alignment, 28(10)% of the maximum possible, is preserved during the separation process allowing the determination of magnetic moments. The measured values of the lifetime, $ \tau$ = 1.54(9) μs, and the g -factor, g = - 0.175(20) , agree with the results of previous investigations using fusion-evaporation reactions.

In-beamγ-ray and conversion electron measurements with (α, xn) reactions have established the145Sm highspin states up toIπ=25/2+ at 3.5 MeV excitation. A shell model analysis using empirical two- and one-body energies from neighbouring nuclei classifies the low-lying odd-parity levels as 3-quasiparticle states formed by the144Sm two-proton-hole excitations and thef7/2 valence neutron. The higher-lying positive-parity states involve particle-hole core excitations with one proton inh11/2.

The level structure of196Po has been studied using a160Dy(40Ar, 4n) reaction and a recoil-catcher technique to reduce fission. The results showed a sharp drop off in the first (2+) and (4+) energies relative to systematics implying an abrupt increase in the quadrupole collectivity at N=112. In addition, second (2+) and(4+) states were identified at 859 and 1388 keV, respectively, suggesting the discovery of a 4p2h deformed band in Po isotopes which is related to known 2p2h proton bands in several Pb isotopes. A prompt183W(20Ne, 5n@#@) experiment located similar second 2+ and 4+ states at 1039 and 1483 keV in198Po providing corroboration and extended information on the properties of the new Po deformed bands. A measured halflife of 850 (90) ns for the 2491 keV (11−) state in196Po implied collective E3 contributions to the extractedB (@#@ E3; 11−→8+)=27(5) W.u.

Yrast- and above-yrast states in149Tb were investigated in (α, 6n) and (7Li, 2n) in-beamγ-ray experiments. The yrastγ-ray cascade strongly populates three-valenceparticle states involving theh 11/2 proton and thef 7/2,h 9/2, or;i 13/2 neutron orbitals, as well as the high-spin levels formed by the couplings of the three149Tb valence particles, to the low-lying146Gd octupole phonon and to higher-lying proton particle-hole core excitations. The data give the (πh 11/2 vi 13/2)12− attraction free of octupole contributions as -631 keV. The shell model with empirical two-particle- and particle-phonon residual interactions gives an excellent quantitative description of the149Tb energy levels. It is noted that the observed highspin members of theπh 11/2 vh 9/2 v f 7/2 configuration closely resemble the lowest symmetric and mixed-symmetry representations of theS 3 permutation group.

We report on a set of in-beam studies of excited states in $^{250}\mathrm{Fm}$. We detected prompt \ensuremath{\gamma} rays by using the JUROSPHERE IV array and conversion electrons by using the SACRED spectrometer. Both devices were used in conjunction with the RITU gas-filled recoil separator located at the University of Jyv\"askyl\"a. $^{250}\mathrm{Fm}$ nuclei were produced through the $^{204}\mathrm{Hg}$($^{48}\mathrm{Ca}$,$2n)$$^{250}\mathrm{Fm}$ fusion-evaporation reaction. An experimental excitation function gave a maximum reaction cross section of (980 \ifmmode\pm\else\textpm\fi{} 160) nb at an energy of 209 MeV in the center of the target. Tagging techniques were employed, and a number of E2 transitions were observed that connected the ground-state band levels from spin ${4}^{+}$ up to ${18}^{+}$. The highly converted ${4}^{+}\ensuremath{\rightarrow}{2}^{+}$ transition is observed only by use of conversion electron spectroscopy. The observed ground-state band transitions indicate a rotational structure. We deduce a quadrupole deformation parameter of ${\ensuremath{\beta}}_{2}=0.28$ \ifmmode\pm\else\textpm\fi{} 0.02. A low-energy background of apparent nuclear origin is observed in conversion electrons and postulated to arise from the decay of high-K bands. The half-life of $^{250}\mathrm{Fm}$ is measured to be 30.4 \ifmmode\pm\else\textpm\fi{} 1.5 min.

High spin states in nuclei in the 208Pb region were populated in deep inelastic collisions of 136Xe and 208Pb projectiles with thick 208Pb targets at about 50 MeV above the Coulomb barrier. Prompt and prompt-delayed γ-ray coincidences were measured. Four new states above the 8+ isomer in 210Pb were found and spins and parities assigned from theoretical expectations. The results are discussed in the frame of shell model theory.

The results are presented from the experiments using the EUROBALL and RFD/HECTOR arrays, concerning various aspects of collectivity in light nuclei. A superdeformed band in 42 Ca was found. A comparison of the GDR line shape data with the predictions of the thermal shape uctuation model, based on the most recent rotating liquid drop LSD calculations, shows evidence for a Jacobi shape transition in hot, rapidly rotating 46 Ti and strong Coriolis eects in the GDR strength function. The preferential feeding of the SD band in 42 Ca by the GDR low energy component was observed

High-spin states of the 44Ca nucleus populated in the 68 MeV 18O + 30Si reaction have been studied in a γ-γ-recoil coincidence experiment. The level scheme of 44Ca has been extended up to 12.2 MeV. In particular, the negative-parity band has been identified with the highest I = 13- level at 10.6 MeV. This state is interpreted as the band-terminating state for the ( d 3/2 -1 f 7/2 5) configuration.

High-spin states in nuclei around 208Pb were populated in deep inelastic collisions of 136Xe and 208Pb projectiles with 208Pb targets at beam energies about 12% above the Coulomb barrier. New states in nuclei in the vicinity of 208Pb have been found that result from the coupling of one and two quasi particles to the lowest 3− excitation of the 208Pb core. They show the influence of particle octupole-vibration coupling in a pronounced and clear way and verify the validity of this concept.

We have deduced for the first time a level scheme for the {sup 199}At nucleus. The angular distribution data and the conversion electron information have allowed for multipolarity assignments and spin suggestions to be made. The current data and the level systematics of odd At isotopes suggest that the first excited state should be isomeric with a lifetime of the order of a microsecond.

High-spin states in 43Ca, 45Sc, and 45Ti were studied with the GASP multidetector array coupled with the Recoil Mass Spectrometer. The nuclei were excited in the 60 MeV 18O +30Si reaction. Lifetimes were extracted from the analysis of the Doppler-shift attenuation of γ-rays observed in the reversed 35Cl+12C reaction. The lifetimes, B(M1) and B(E2) values for 45Sc are presented. The measurements suggest significant deformation of the positive-parity intruder band in this nucleus. The band is predicted by the mean-field calculations to be the cross-shell particle-hole excitation associated with a strong quadrupole core-polarization. Spherical shell-model calculations reproduce observed excitation energies and transition rates in both spherical and deformed structures.

Intruder rotational bands in 45 Sc and 45 Ti have been investigated up to the maximum aligned angular momentum by means of EUROBALL IV and the Recoil Filter Detector (RFD). The use of the RFD allowed for a reduction of the $\gamma$ -line Doppler broadening and, moreover, for a determination of very short level lifetimes. In the studied nuclei, the estimated deformation shows a gradual disappearance of the collectivity at the highest available spins.

The 13/2+ isomeric state in the 199At nucleus has been identified at an excitation energy of 573 keV and its half-life measured to be 580(130) ns using the recoil-decay tagging technique.

In-beamγγ- andγγn-measurements have for the first time identified excited states in the 72 157 Hf85 nucleus and have established its yrast levels up to 6.5 MeV and I=(51/2). The results of parameter-free 11-particle recoupling calculations in the framework of the shell model for the configurationsπh 11 2/8 νf 7 2/3 andπh 11 2/8 νf 7 2/2 h9/2 are in excellent agreement with the observed levels up to 39/2 at 4.758 MeV. A weakly populated 52 ns 29/2+ yrast isomer at 2.876 MeV is assigned as the three-neutron configurationνf7/2h9/2i13/2.

In (α,5n) in-beam γ- and electron measurements we have established high-spin states in the 3-neutronhole nuclei141Sm and143Gd. Observed energy levels below 4 MeV are interpreted in terms of shell model configurations where the odd h11/2 neutron hole couples to the N=80 core excitations containing one h11/2 proton particle or one h11/2 neutron hole. Higher-lying yrast states are built on a 23/2− level at Rd 3.2 MeV probably involving the πh12/2guh112/−1 configUTa-tion.

The N=84 nucleus154Yb was investigated through the106Cd(54Fe,α2p) reaction. We found the 16+ yrast level in this nucleus to be formed by the (πh11/22νf7/2h9/2) configuration, in contrast to the lower-Z isotones where (πh11/22νf7/22)16+ is the yrast state. Manybody shell model calculations with empirical two-body interactions support our conclusion.

In the two-valence-neutron nucleus /sup 148/Gd, in-beam /sup 148/Sm(..cap alpha..,4n) and (/sup 3/He, 3n) measurements have identified nine ..nu.. /sup 2/ x octupole levels with 3..6/sup +/) = 55(6)B/sub W/ . A high-lying 12/sup +/ level, which decays by E3 to the 9/sup -/ state, as well as a 14/sup +/ level are shown to be two-phonon octupole excitations of stretched ..nu.. /sup 2/ x 3/sup -/ x 3/sup -/ character. All these results can be quantitatively derived from the experimental data for the coupling of one neutron to the core octupole observed in /sup 147/Gd.

Excitation function measurements with α-particles and HI-beams clearly attribute the yrast cascade previously proposed for142Gd to the141Eu neighbouring nucleus. The so far unknown yrast transitions of142Gd have been identified. Coincidence measurements establish the high-spin level schemes of the two nuclei up to 3.2 MeV.

The neutron deficient 199At nucleus has been studied in the 175Lu+28Si reaction at Eb= 141 MeV. In order to select events of interest in the presence of the very strong background caused by fission, γ-rays have been detected in coincidence with recoiling evaporation residues. The excited states of 199At observed for the first time may indicate that this nucleus is deformed.

An (α,p6n) in-beam γ-ray experiment has established the high-spin states of the N=78 nucleus141Eu up to I=35/2− at 4.4 MeV excitation. The levels above 3 MeV involve the couplings of the h11/2 valence proton to either two aligned h11/2 proton particles or two aligned h11/2 neutron holes. The observed spin sequences are in accord with the shell model for these couplings.

In-beam studies with (α,4n) and (3He, 3n) reactions have located a second 10+ state closely above the 10+ isomers in144Gd and142Sm. The data characterize the142Sm 10+ isomer as the νh 11 2/−2 excitation in contrast to144Gd where the 10+ isomer is of πh 11 2/2 character.

An in-beam γ-ray study with the144Sm (α, p4n) reaction has established the high-spin states up to 5 MeV excitation and I=35/2 in the N=80 nucleus143Eu. The observed yrast states show the typical irregular pattern of a spherical nucleus, with frequent decay branchings and often dominant dipole de-excitation. The level spectrum is in qualitative accord with the coupling of the h11/2 proton particle to the known yrast levels of the142Sm core nucleus. Only in a few cases specific configuration assignments are made.