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High-spin states of doubly odd 218 Ac1 129 have been investigated using in-beam α, γ and conversion electron spectroscopy techniques through the 209 Bi( 12(13) C,3(4)n) fusion-evaporation reactions. The level scheme of 218 Ac shows three interconnected, alternating parity structures, each one linked by strong El transitions. Two of these bands are strikingly similar to the known scheme of the isotone 217 Ra and this analogy is shown to persist for the pair 220 Ac, 219 Ra. The relation between the structure of 218 Ac and its neighbors is thoroughly discussed showing that the first signals of octupole collectivity appear for N = 129.

Coupling schemes which lead to very similar structures in doubly odd, odd and even even nuclei, discovered in the normal‐deformation regime, are reviewed and applied to the problem of identical superdeformed bands. It is shown that such schemes, using as an additional ingredient pseudospin alignment, provide a natural frame to understand this problem.

The study of doubly odd nuclei has become a subfield of nuclear structure in its own right. A large body of data has been accumulated and we shall attempt in this work an approximation to a review. This however has to be qualified, otherwise the scope of the subject would be unmanageably extensive. We shall concentrate ourselves on near-yrast states of deformed and transitional nuclei and hence to studies carried out predominantly, though not exclusively, through the (HI, xnypzα) reaction. Some nice examples of how high-spin and low-spin work complement each other will also be given.

Low-spin states of 186 Ir populated through the β + /EC decay of 186 Pt nuclei were studied using mass-separated sources and γ-ray and e − spectroscopic techniques. A completely new level scheme of 186 Ir is established. It is shown that the 2 − isomeric state is located at an energy less than 1.5 keV above the 5 + ground state. A very low-energy transition from the 2 − isomer to the 5 + ground state has to exist in order to explain the data, and its relative intensity has been estimated to be around 25% of the total decay of the 2 − state. Most of the experimental levels are interpreted within the two-quasiparticle-plus-rotor model.

Using coupling schemes derived for low-lying structures in doubly odd deformed nuclei in the framework of the particle rotor model and properties of orbitals which follow from pseudospin symmetry, likely explanations are given for identical superdeformed bands.

When decoupled proton and neutron orbitals combine in doubly-odd nuclei, one obtains a special type of collective structure called a “doubly-decoupled” band. A particle-plus-rotor and cranking model analysis provide a qualitative understanding of all the special features of these bands, showing that strong coriolis effects dictate their main behavior, while the p-n residual force seems to be much less important. They display additivity of striking accuracy for alignments and inertia parameters. Several of these bands have been followed beyond the first band crossing, showing again additivity for the shift in crossing frequency. These properties may raise questions concerning the deformation-driving tendency of the πh 9/2, orbital and on the exclusive vi 13/2 origin of the first backbend.

Excited states of220Ac have been investigated by means of the209Bi(14C,3n) reaction and using the “Château de Cristal” gamma ray facility. The observation of bands with alternating parity states reveals the reflection asymmetric nuclear shape of220Ac. The extracted B(E1)/B(E2) ratios display a clear spin dependence.

High-spin states in 124Xe were populated by means of the 110Pd(18O,4n) reaction. In-beam γ rays were measured using the GASP spectrometer. A dipole band, similar to those previously found in other nuclei of this mass region, was identified in 124Xe.

High spin rotational bands in 162 Lu and 164 Lu have been studied through the 139 La( 28 Si,5n) and 139 La( 29(30) Si,4(5)n) reactions respectively. For both nuclei the yrast sequence which is associated with the πh 11/2 ⊗νi 13/2 configuration shows the signature inversion feature.

Low-spin states in doubly-odd184Au have been populated in the β+/EC decay of184Hg produced by bombarding184Sm targets with an 185 MeV40Ar beam. Radioactive Hg nuclei were transported by a He jet system. A new level scheme has been established from γ-γ-t and X-γ-t coincidence measurements. Spin and parity values Iπ=5+, Iπ =2+ and Iπ=3− were assigned to the ground state and the two isomeric states of184Au, respectively. The structure of these states is discussed using B(E1) values.

An analytical characterization of the conditions for double decoupling in doubly odd deformed nuclei is given within the framework of the rotational mode. The stimulus for this investigation originates in the observation of a band in /sup 186/Ir, which is possibly the first case where such a coupling scheme is realized.

States of /sup 200/Tl, populated through the /sup 198/Pt(/sup 6/Li,4n) reaction at E=30 to 40 MeV, were studied using in-beam ..gamma..-ray spectroscopy techniques. An almost completely new level scheme is presented comprising the pi-tildeh/sub 9/2/xnu-tildei/sub 13/2/ two-quasiparticle band which in this case is built on an I/sup ..pi../=7/sup -/ isomeric state (T/sub 1/2/=4.8 +- 0.2 ns) in contrast to I/sup ..pi../=8/sup -/ for all the lighter doubly odd Tl isotopes studied up to now. The systematic variation of the odd-even staggering present in these bands offers arguments to support the interpretation that this phenomenon is related to the signature dependence of the Coriolis interaction.

High-spin states of 100Rh have been populated with the reactions 99Ru(α, 2np) and 98Mo(6Li, 4n) and their γ-decay has been studied with Ge(Li) detectors in singles and coincidence. Angular and time distributions of the γ-rays were also measured. As a result 14 new levels spanning spins up to I = 16 built on the 5+, 4.5 min isomer at 107 keV have been established, and a half-life of T 1 2 = 120 ± 5 nsec has been determined for the 7+ state at 111.9 keV. The rotor-plus-two-quasiparticle model has been used to describe the observed level structure. The pn interaction is shown to be of negligible effect. On the other hand, the introduction of a soft core is essential. The application of the VMI model with the parameters extracted from the 98Ru core yields a remarkably good agreement. This is the first time that the anomalous VMI root ( I 0 has been applied to a doubly odd nucleus.

High spin states in /sup 86/Y were studied through the /sup 85/Rb(..cap alpha.., 3n) reaction at energies between 30 and 55 MeV, using techniques of in-beam ..gamma..-ray spectroscopy. Eight levels were observed on top of the J/sup ..pi../ = 8/sup +/ (218.3 keV) metastable state which are connected by ..gamma.. rays in cascade and five levels decaying to the J/sup ..pi../ = 5/sup -/ (208.1 keV) excited state. The former were interpreted in terms of the weak coupling of the proton ..pi..(1g/sub 9/2/) and the neutron hole ..nu../sup -1/(1g/sub 9/2/) coupled to the /sup 86/Sr excited states on the basis of the shell model.

Isomeric transitions, of E3, M2, and E1/M2 character, depopulating pi-tildeh/sub 9/2/xnu-tildei/sub 13/2/ bands in /sup 186,188,190/Tl, respectively, have been found with use of ..gamma..-ray spectroscopic techniques. The changes in multipolarity reflect successive changes in the bandhead spin values corresponding to level crossings within the pi-tildeh/sub 9/2/xnu-tildei/sub 13/2/ system. These crossings were predicted in the framework of the two-quasiparticle plus rotor model and interpreted as a direct consequence of the depletion of the i/sub 13/2/ shell.

Rotational bands in the odd-odd nucleus $^{180}\mathrm{Re}$ have been studied via the $^{176}\mathrm{Yb}$${(}^{10}$B,6n) and $^{181}\mathrm{Ta}$(\ensuremath{\alpha},5n) fusion-evaporation reactions. A completely new high-spin level scheme has been obtained comprising four \ensuremath{\Delta}I=1 bands and a \ensuremath{\Delta}I=2 band. The \ensuremath{\Delta}I=1 structures can be understood from quasiparticle states in neighboring odd nuclei and the \ensuremath{\Delta}I=2 band is interpreted as a new example of a double decoupled sequence based on the decoupled ${h}_{9/2}$ proton and a ${(1/2}^{\mathrm{\ensuremath{-}}}$[521] neutron. The different coupling schemes in a deformed doubly odd nucleus are discussed.

States of /sup 74/Br excited through the /sup 60/Ni(/sup 16/O,np) reaction at E = 40 to 55 MeV were studied. From the excitation function, ..gamma..-ray angular distribution, ..gamma..-..gamma.. coincidences, and decay measurements three groups of ..gamma.. rays depopulating states with probable spin values ranging up to I = (11) were found. A half-life of 49.5 min and I = (4) for the high spin isomeric state at Eroughly-equal200 keV were determined at variance with previous values of 41.5 min and I = (4/sup -/). The group of ..gamma.. rays feeding the I = (4) isomer shows similarities with a recently reported band built on a 4/sup +/ isomer in both /sup 76/Br and /sup 78/Br. The interpretation of these states as members of the ..pi..g/sub 9/2/x..mu..g/sub 9/2/ structure is discussed.

States of 184Ir, excited through several (HI, xn) reactions were studied using in-beam γ-ray and conversion electron spectroscopy techniques. A new high-spin level scheme, comprising three different rotational bands is presented. The negative-parity ΔI = 1 ground-state band is the most complete example of the semidecoupled \ gp h 9 2 ⊗ v i 13 2 structure, in a prolate deformed situation, known to date. The other two bands are the doubly decoupled \ gph 9 2 ⊗ v 1 2 − [521] and a ΔI = 1, \ gp 5 2 + [402]⊗v i 13 2 based structure of the compressed type.

The parity of high-spin states in the N = 55 isotones 98Tc and 100Rh has been determined by means of in-beam measurements of electron conversion coefficients. A ΔJ = 1 negative-parity band based on a Jπ = 8- state has been identified in both nuclei. The observed bands, similar to those of odd-odd Ag isotopes, can be interpreted as due to the coupling of a g9/2 proton configuration with a neutron in the h11/2 subshell.

An investigation of the collective structures in the doubly-odd nucleus $^{132}\mathrm{Pr}$ has been undertaken with the $^{117}\mathrm{Sn}$${(}^{19}$F,4n${)}^{132}$Pr reaction. Two distinct rotational structures showing both signature components have been established. One band, with no signature splitting, is built on a near-prolate \ensuremath{\pi}${h}_{11/2}$\ensuremath{\bigotimes}\ensuremath{\nu}${g}_{7/2}$ structure. The second band, with a small signature splitting, involves the \ensuremath{\pi}${h}_{11/2}$\ensuremath{\bigotimes}\ensuremath{\nu}${h}_{11/2}$ configuration with a triaxial shape. A comparison with recent results for the $^{130}\mathrm{La}$ isotone has been made. A third band structure of large signature splitting (doubly decoupled) was observed showing only one signature component. This band structure is believed to involve the \ensuremath{\beta}-driving \ensuremath{\nu}${i}_{13/2}$${[660](1/2}^{+}$ orbital.

High spin states of /sup 75/Br were studied through the /sup 62/Ni (/sup 16/O,2np) reaction. A positive and a negative parity band were established up to spin (25/2). A new low-lying isomeric (9/2/sup +/) state (T/sub 1/2/ = 39 +- 4 ns) at 220.6 keV excitation energy, most likely of pi-tildeg/sub 9/2/ parentage, was found. The structure was interpreted in the light of the one quasiparticle plus rotor model concluding that the quadrupole deformation is largest for /sup 75/Br compared to all other known odd Br isotopes.

Evidence is discussed for a predicted change of phase in the odd-even level staggering, at a certain spin value, of Coriolis-distorted bands in doubly-odd transitional nuclei. Examples are given, covering different regions of the nuclidic chart, for the likely occurrence of similar phenomena.

The level scheme of $^{98}\mathrm{Tc}$ has been investigated via the $^{94}\mathrm{Zr}$${(}^{7}$Li,3n\ensuremath{\gamma}) reaction by in-beam \ensuremath{\gamma} spectroscopy and conversion-electron measurements. Gamma ray excitation functions, \ensuremath{\gamma}-\ensuremath{\gamma} coincidences, and ${I}_{\ensuremath{\gamma}}$(0\ifmmode^\circ\else\textdegree\fi{})/${I}_{\ensuremath{\gamma}}$(90\ifmmode^\circ\else\textdegree\fi{}) anisotropies have been measured in the energy interval ${E}^{\mathrm{*}}$${(\mathrm{}}^{7}$Li)=23--31 MeV. High spin states up to I=14 and ${E}^{\mathrm{*}}$=3200 keV have been observed. A \ensuremath{\Delta}I=1 negative parity band based on the ${I}^{\ensuremath{\pi}}$${=8}^{\mathrm{\ensuremath{-}}}$, 1091 keV state has been identified. The level scheme has been compared with the predictions of the two quasiparticles plus rotor model. The negative parity band is associated with the \ensuremath{\pi}\ifmmode \tilde{}\else \~{}\fi{}${g}_{9/2}$\ensuremath{\bigotimes}\ensuremath{\nu}\ifmmode \tilde{}\else \~{}\fi{}${h}_{11/2}$ intrinsic configuration space.

High-spin states in /sup 192/Tl, excited through the /sup 181/Ta(/sup 18/O,7n) and /sup 181/Ta(/sup 16/O,5n) reactions, were studied using in-beam ..gamma..-ray spectroscopic techniques. Excitation functions, activity spectra, ..gamma..-ray angular distributions, and multidimensional coincidences were measured. The strongly Coriolis-distorted pi-tildeh/sub 9/2/ x nu-tildei/sub 13/2/ two-quasiparticle band already known in the heavier /sup 194,196,198/Tl isotopes has also been found in this case based on an I/sup ..pi../=8/sup -/ isomeric state at 250.6 keV above the known long-lived 7/sup +/ level. Trends already noted in the other Tl isotopes and also predicted by two-quasiparticle plus-rotor model calculations are confirmed thus reinforcing such a theoretical description.

The deexcitation of states in 188 Ir, formed through the 187 Re(α, 3n) 188 Ir reaction, was studied using in-beam and off-beam gamma and electron spectroscopy techniques. A new level scheme, exhibiting a rather high level density, is presented. An interpretation of the structure of these states is attempted using information on one-quasiparticle intrinsic states from neighboring oddproton and odd-neutron nuclei.

High-spin states in 78Br decaying into the 4+ isomer at 180.8 keV were excited via the 77Se(α, 2np) and 76Ge (7Li, 5n) reactions. A sequence of closely lying levels with I ⩽ 8 is found between 227.6 and 467.6 keV. The highest state in this group is populated by a relatively strong 904.1 keV ΔI = 2 transition. These features provide a basis for a comparison with the positive-parity ground-state Coriolis-distorted band of 79Kr, in the light of a rotor plus one- and two-quasiparticle descriptions. Other previously reported low-spin states are also seen weakly with this reaction. Two new isomeric states of 9±1 ns at 337.8 keV and 84±8 ns at 227.6 keV are found. The latter decays into the 4+ isomer through a 46.8 keV transition, which lies unresolved from the 46.3 keV line. The existence of this doublet explains an earlier discrepancy.

States in doubly odd /sup 218/Ac have been studied using in-beam ..cap alpha..-, ..gamma..-, and e/sup -/-spectroscopy techniques mainly through the /sup 209/Bi(/sup 12/C,3n)= fusion-evaporation reaction. /sup 218/Ac shows a band structure, with interleaved states of alternating parities connected by enhanced B(E1) transitions, which is strikingly similar to the one in its isotone /sup 217/Ra.

The recent announcement of electrochemically induced nuclear fusion [1,2] has generated great interest and activity within the scientific community. In particular, there are several aspects related to the work of ref. 1 which are not fully understood and therefore deserve further investigation. One of them is the huge discrepancy between the amount of measured heat and the intensity of the supposedly accompanying nuclear radiation, namely neutrons and gamma rays. In view of the fact that the detection of nuclear radiation in the context of an electrochemical process is perhaps the most unequivocal fingerprint for the occurrence of fusion, we feel that a careful re-evaluation of the measurement conditions may be needed. In order to address this question, in the present paper we report on an attempt to observe this phenomenon and on the possible problems related to the detection techniques.

The nature of the first band crossing in the heavy rare-earth region is an important open spectroscopic problem. Both {ital h} 9/2 protons and {ital i} 13/2 neutrons are likely to be responsible for this phenomenon. The results of a double blocking experiment in {sup 178}Re strongly suggest that in fact a pair of {ital h} 9/2 protons and of {ital i} 13/2 neutrons are simultaneously playing a role.

Rotational bands in the odd-odd nuclei $^{176}$,178Re have been studied via the fusion-evaporation reactions $^{169}\mathrm{Tm}$${(}^{12}$,13C,xn). Several rotational bands have been identified for both isotopes. Techniques of gamma and internal conversion electron spectroscopy have been used. The different band structures are discussed in the frame of the two-quasiparticle-plus-rotor and cranking models.

A 4+, 1.3 s isomer has been found at 102.6 keV in 76Br using the 75As(α, 3n) reaction. A previously reported band structure is interpreted to decay into this isomer of probable π g 9 2 ⊗ ν g 9 2 parentage.

160, 162Tm nuclei have been reinvestigated at high spins by128, 130Te(37Cl, 5n) reactions, respectively. In the yrast bands of both nuclei the crossing frequencies correspond to the second neutron backbending (BC). The same is true for the side bands in162Tm but not in160Tm where the first neutron backbending(AB) is observed.

The transitional doubly‐odd iridium nuclei with A=184 and 186 have been studied from the β+/EC decay of the corresponding platinum isotopes using the on‐line mass separator ISOCELE. Configurations can be reasonably Attributed to the low‐lying states of 184Ir in agreement with results already known. On the other hand an E3 transition observed in 186Ir suggests that the known long‐lived 1.7h 2− state is located at 137.5 keV above the 16h 5+ state, raising questions about structure of this latter state.