Search for decoupled bands in Odd-Odd 174Re

An effort has been made to search for the decoupled bands in odd-odd ¹⁷⁴Re via the ¹⁵⁹Tb(²⁰Ne,5n γ)¹⁷⁴Re reaction through excitation functions, K x-γ and γ-γ coincidence measurements. The doubly decoupled band and the semidecoupled one have been found in this work. Their quasiparticle configurations are proposed to be π1/2⁻[541] ⊗ν1/2⁻[521] and π1/2⁻[541] ⊗νi _13/2, respectively, according to the characteristics of band structures in this mass region. Another band with strongly coupled character is also reported. Received: 23 November 1999 / Revised version: 5 January 2000     

High-spin states in odd-odd 168Lu

High-spin states in the odd-odd ¹⁶⁸Lu nucleus, populated in the ¹⁵⁴Sm(¹⁹F,5n) reaction at a beam energy of 96 MeV, were investigated using in-beam γ-ray spectroscopy techniques. The BC neutron crossing in the yrast band, based on πg _7/2[404]7/2⁺⊗νi _13/2[642]5/2⁺ configuration, occurs at ħω= 0.31 MeV. The two side bands, based on πh _11/2[514]9/2⁻⊗νi _13/2[642]5/2⁺ and πh _9/2[541]1/2⁻⊗νi _13/2[642]5/2⁺ configurations, show anomalous signature-splitting and signature-inversion in the first one, to occur at ħω= 0.24 MeV. A moderately delayed BC-crossing is anticipated in the second one. Received: 15 June 1998 / Revised version: 11 January 1999     

T-band phenomena in 183Re

Abstact: High-spin states in ¹⁸³Re have been studied using the ¹⁷⁶Yb(¹¹B,4n) reaction at 52 and 57 MeV. Two high-K bands have been observed directly by a time-correlated γ-γ coincidence measurement. One of the bands is built on an isomeric K ^π=(25/2)⁺ state at E _x= 1908 keV with a half-life of 0.82(2) ms. The other band, assigned as K ^π=(29/2)⁻ at E _x= 2739 keV, decays to the (25/2)⁺ band. These bands are interpreted as three-quasiparticle structures, π(5/2)⁺[402] &⊗ν(9/2)⁺[624] ⊗ν(11/2)⁺[615] for the (25/2)⁺ band and π(9/2)⁻[514] ⊗ν(9/2)⁺[624] ⊗ν(11/2)⁺[615] for the (29/2)⁻ band. The K ^π= (29/2)⁻ band becomes strongly Coriolis mixed with increasing spin and is gradually changing into a low-K s-band structure. Received: 20 April 1998     

Observation of signature inversion in odd-odd 178Ir

High spin states in ¹⁷⁸Ir have been studied via the ¹⁵²Sm(³¹P, 5nγ)¹⁷⁸Ir reaction through excitation functions, X-γ and γ-γ-t coincidence measurements. According to the band structure characteristics and the measured intraband B(M1)/B(E2) ratios, two rotational bands are identified and assigned to be associated with the πh _9/2⊗νi _13/2 and πh _11/2⊗νi _13/2 configurations, respectively. Both bands show the signature inversion feature. Received: 23 March 2000 / Accepted: 31 July 2000     

High-spin states of rotational bands built upon νi13/2 in 166Lu

High-Spin states of odd-odd ¹⁶⁶Lu were populated using the ¹³⁹La(³⁰Si,3nγ)¹⁶⁶Lu at a beam energy of 120 MeV. Twelve new γ-rays were placed on top of the previously known two rotational bands built upon πg _7/2⊗νi _13/2 and πh _11/2⊗νi _13/2. Extending high-spin states up to 21⁺ and 25⁻ for each band, we have observed the onset of band crossing near ħω _c ≈ 0.35 MeV. The band crossing frequency of the yrast πh _11/2⊗νi _13/2 band is consistent with the neutron BC band crossing observed in lighter odd-odd Lu isotopes.     

Conservation laws for classical and relativistic collisions. II

On the basis of elementary symmetry arguments it is shown that (1) if in classical mechanics there exists a quantity λ+Σ_iμ_iυ_i+1/2νυ ² that is conserved, where λ,μ _i, andν are particle parameters, then theμ _i andν are all proportional to a single parameterμ and the quantityAμ+Σ_iB_iμυ_i+C(λ+ 1/2Dμυ ²), whereD ≡ν/μ, is conserved for all values ofA, B _i, andC; (2) if in relativistic mechanics there exists a quantity λ+Σ_iμ_iυ_i[1−(υ ²/c ²)]^−1/2+νc[1−(υ ²/c ²)]^−1/2 that is conserved, then theμ _i andν are all proportional to a single parameterμ and the quantityAλ+Σ_iB_iμν_i[1−(υ ²/c ²)]^−1/2+Cμc [1−(υ ²/c ²)]^−1/2 is conserved for all values ofA, B _i, andC.     

High-spin states in odd-odd 168Lu

High-spin states of odd-odd ¹⁶⁸Lu were observed up to 18ħ for the first time using the ¹⁵⁹Tb(¹³C, 4nγ)¹⁶⁸Lu reaction at E _13C= 58.5 MeV. γ-γ coincidence, E _γ singles, excitation function, and the DCO ratios were measured. Two rotational bands with signature splitting were populated, among which the lower-energy band is identified as π 7/2⁺[404] ⊗ν 5/2⁺[642] in view of alignment and energy systematics. Received: 27 October 1997     

High spin states and evidence for octupole correlations in 117Xe

High-spin states of ¹¹⁷Xe were investigated by means of in-beam γ-ray spectroscopic techniques via the reaction of ²⁸Si bombarding a ⁹²Mo target at beam energies of 100-120 MeV. A positive-parity rotational band decaying into the yrast negative-parity band by a series of enhanced E1 transitions was observed for the first time, implying the existence of octupole correlations in ¹¹⁷Xe. The B(E1) values increase with spin. The νd_5/2 band was firmly established up to 27/2⁺ and the B(M1)/B(E2) ratios were extracted from the relative intensities of γ-rays in this band. The previously known νh_11/2 and νg_7/2 [413]5/2⁺α=−1/2 bands were confirmed and extended up to high spins and two bandcrossings are observed in the latter at ħω=0.33 and 0.44 MeV, respectively. The bandcrossings and configurations of these bands are discussed by TRS and CSM calculations. In a γ–γ–t measurement, the 11/2⁻ and 7/2⁻ levels were identified as two isomers with half-lives of 59.4±20 ns and 16.5±8.0 ns, respectively. Received: 17 June 1997 / Revised version: 29 September 1997     

Yrast bands in N = 91 isotones

The in-beam spectroscopy on N = 91 isotones has been carried out using the ¹²C + ¹⁵⁰Nd reaction. The νi _13/2 and νh _11/2 bands of ¹⁵³Sm have been extended up to 33/2⁺ and 31/2^-, respectively. Two new γ-rays have been located on the top of the unfavored band with νi _13/2 configuration in ¹⁵⁷Dy. Two identical relationships have been established in the low-spin region of the yrast νi _13/2 configuration between ¹⁵³Sm and ¹⁵⁵Gd, and between unfavored bands of ¹⁵⁵Gd and ¹⁵⁷Dy. Here all these nuclei have the same neutron number N = 91. Received: 28 June 2000 / Accepted: 20 October 2000     

Shape co-existence and structural evolution of the yrast band in 157Yb

The high-spin states of ¹⁵⁷Yb have been studied via the ¹⁴⁴Sm(¹⁶O, 3n) reaction at ¹⁶O energy of 90 MeV using techniques of in-beam γ-ray spectroscopy. Measurement of γ-γ-t coincidences was performed with 11 BGO(AC)HPGe detectors. Based on the measured results of γ-γ coincidences, γ-ray anisotropies and DCO ratios, the level scheme for ¹⁵⁷Yb was established. The shape co-existence and structural evolution of the νi _13/2 band with increasing angular momentum in ¹⁵⁷Yb have been discussed. The systematics of the νi _13/2 bands in the N = 87 odd-A isotones have been compared. Received: 7 January 2002 / Accepted: 10 April 2002     

High-spin states and signature inversion in odd-odd182Au

High-spin states in¹⁸²Au have been produced and studied via the¹⁵²Sm(³⁵Cl,5nγ)¹⁸²Au reaction. The level scheme consisting of the πh _9/2⊗νi _13/2 and πi _13/2⊗νi _13/2 bands has been established for the first time. The low spin signature inversion in both bands has been found. The observed signature inversion phenomena can be interpreted qualitatively using the pairing and deformation self-consistent cranked Wood-Saxon calculations.     

Observation of a πh9/2 ⊗ νi13/2 oblate band in 188Tl

Excited states in ¹⁸⁸Tl have been studied experimentally using the ¹⁵⁷Gd (³⁵Cl, 4n) reaction at a beam energy of 170MeV. A rotational band built on the πh _9/2 ⊗ νi _13/2 configuration with oblate deformation has been established for ¹⁸⁸Tl. Based on the structure systematics of the oblate πh _9/2 ⊗ νi _13/2 bands in the heavier odd-odd Tl nuclei, we have tentatively proposed spin values for the new band in ¹⁸⁸Tl. The πh _9/2 ⊗ νi _13/2 oblate band in ¹⁸⁸Tl shows low-spin signature inversion, and it can be interpreted qualitatively by the two-quasiparticle plus rotor model including a J-dependent p-n residual interaction.     

Signature inversion in πi13/2⊗νi13/2 structure in 178Ir

High-spin states in ¹⁷⁸Ir were investigated by means of in-beam γ-ray spectroscopy techniques using the multidetector array GASP. Excited states of ¹⁷⁸Ir were populated through the ¹⁵⁹Tb(²⁴Mg, 5n) fusion-evaporation reaction at E(²⁴ Mg) = 131-141 MeV. Several rotational bands were observed. Among them, the πi _13/2⊗νi _13/2 structure has been identified up to spin 36 ?. This band exhibits an anomalous signature splitting and a signature inversion around spin 25 ?. Received: 13 December 2000 / Accepted: 11 April 2001     

Conservation laws for classical and relativistic collisions. I

On the basis of simple kinematic arguments it is shown that any quantity, depending only on the nature and velocity of a particle, that is conserved in a collision must, in classical mechanics, be of the form λ+Σ_iμ_iυ_i+1/2vυ ² or in relativistic mechanics of the form λ+Σ_iμ_iυ_i[1−(υ ²/c ²)]^−1/2+νc [1−(υ ²/c ²)]^−1/2 where λ,μ _i, andν are particle parameters.     

Investigation into the rotational bands of 185Pt with the particle-rotor model

Theoretical calculations have been performed for the ν9/2⁺[624](i _13/2) and ν7/2⁻[503]( f _7/2) bands of ¹⁸⁵Pt in the framework of particle-rotor model. The band properties of signature splitting and configuration mixing have been analyzed. The level energy and signature splitting before the band crossing can be well interpreted by introducing triaxiality. The positive-parity yrast band is proposed to be dominated by the ν9/2⁺[624](i _13/2) component, while the negative-parity band shows strong mixing of ν7/2⁻[503](f _7/2) and ν9/2⁻[505](h _9/2) configurations.

     

Shape co-existence and structural evolution of thevi13/2 band in157Yb

The high-spin states of¹⁵⁷Yb have been studied via the reaction of¹⁴⁴Sm(¹⁶O, 3n) at¹⁶O energy of 90 MeV using techniques of in-beam γ-ray spectroscopy. Measurement of γ-γ-t coincidences was performed with 11 BGO(AC)HPGe detectors. Based on the γ-γ coincidence relationships and the measured results of γ-ray anisotropies and DCO ratios, the level scheme for¹⁵⁷Yb was established. The shape co-existence and structural evolution of thevi_13/2 band with increasing angular momentum in¹⁵⁷Yb have been discussed. The systematics of thevi_13/2 bands in theN=87 odd-A isotones have been compared.     

Rotational structures in the 125Cs nucleus

The collective band structures of the ¹²⁵Cs nucleus have been investigated by in-beam γ-ray spectroscopic techniques following the ¹¹⁰Pd ( ¹⁹F, 4n) reaction at 75MeV. The previously known level scheme, with rotational bands built on πg_7/2, πg_9/2 and πh_11/2 orbitals, has been extended and evolves into bands involving rotationally aligned ν(h_11/2)² and π(h_11/2)² quasiparticles. A strongly coupled band has been reassigned a high-K πh_11/2 ⊗ νg_7/2 ⊗ νh_11/2 three-quasiparticle configuration and a new side band likely to be its chiral partner has been identified. Configurations assigned to various bands are discussed in the framework of Principal/Tilted Axis Cranking (PAC/TAC) model calculations.     

High-spin states in 160Lu

High-spin states of ¹⁶⁰Lu have been studied through the ¹⁴⁴Sm( ¹⁹F, 3n) reaction. The previously known πh _11/2⊗υi _13/2 yrast band is extended from I ^π = 21^- to 25^- and a four quasiparticle band with configuration πh _11/2[523]7/2 ^-⊗υh _9/2[521]3/2 ^-⊗ (υi _13/2)² is reported. Received: 21 May 2001 / Accepted: 19 July 2001     

Characterization of quasiparticle states at and beyond stability in ytterbium isotopes: Spectroscopy of 175Yb, 176Yb and 177Yb

Excited states in ¹⁷⁵Yb, ¹⁷⁶Yb and ¹⁷⁷Yb were populated via the bombardment of a ¹⁷⁶Yb target with a 750 MeV ¹³⁶Xe beam. Gamma-ray decays from these states were measured with the AFRODITE multi-detector spectrometer. The rotational band previously assigned to the ground state of ¹⁷⁷Yb has been reassigned to the first-excited state of ¹⁷⁵Yb. A new rotational band based on the ground state of ¹⁷⁷Yb is presented, and the band based on the K^π = 4^- two-quasiparticle state in ¹⁷⁶Yb has been identified. Also a candidate for the rotational band based on the K^π = 8^-, T_1/2 = 11.4(3) s two-quasiparticle state in ¹⁷⁶Yb has been found. Comparisons of g_K values derived from in-band branching ratios are consistent with the ν9/2⁺[624] assignment to the ground state of ¹⁷⁷Yb, the ν²{9/2⁺[624] ⊗ 1/2^-[510]} assignment to the K^π = 4^- state and with the ν²{9/2⁺[624] ⊗ 7/2^-[514]} assignment to the K^π = 8^- metastable excited state in ¹⁷⁶Yb.     

Optical absorption spectrum of Cr3+ in natural ruby

Two sharp line-like bands calledN andR lines on the red side, a close doublet (B lines) on the violet side and two broad bands are observed for natural ruby. At liquid air temperature the splitting ofR line was found and also three sharp-bands calledR, R′ andB lines are identified with spin-forbidden transitions of² E,² T ₁ and² T ₂. The two broad bands calledU band andY band are assigned accordingly to the spin-allowed transitions⁴ T ₂ and⁴ T ₁ respectively. The observed bands of natural ruby have been attributed to Cr³⁺ ion in an octahedral environment with trigonal distortion. The crystal field parameters which gave a good fit to the observed band positions areB=732 cm⁻¹,C=4.25B,Dq=1830 cm⁻¹,V=−1996 cm⁻¹ andλ=34 cm⁻¹.