Shape coexistence

It is important to understand what gives rise to the established coexisting intruder band in doubly closed subshell 9(>Zr. The slight predominance of the intruder deformed configuration in the ground state wavefunction of lO Mo shown in Fig. 1(b) cannot explain the tremendous difference between the alpha-pickup strengths to the two 0+ states of 9 >Zr clearly demonstrated by Fig. 1(a). This is not unexpected, since the simultaneous occurrence of proton and neutron subshell closures should produce a marked difference with respect to other nuclei near the middle of the 50 to 82 neutron shell where two-proton, two-hole excitations can account entirely for the observed shape coexistence phenomena. 

The structures of the neutron-rich isotopes 97Y, 98Y and 99Y reflect with special clearness the rapid change of the nuclear shape at neutron number 60. The discovery of a new isomer in 97Y has provided evidence for the shell-model character of this nucleus even at high excitation energies while 99Y shows the properties of a symmetric rotor already in the ground state. The level pattern of the intermediate isotope 98Y indicates shape coexistence. 

Conclusions We have established that the light Br and Rb isotopes presented here have very large quadrupole deformations of s 0.4 and moments of inertia close to the rigid body values. The odd proton in the 431 3/2+ Nilsson orbit polarizes and stabilizes the y-soft, shape coexistent Se and Kr cores into definite prolate triaxial shapes. This effect sets in at rather low spin and seems to be intimately connected with the suppression of pairing correlations near the N = Z = 38 gap developing at 82 = 0.4. We thus face a cumulative suppression of both proton and neutron pairing correlations in the same oscillator shell, a fairly unique feature in the periodic table. 

The energy level spacings of the 0+-2+-4+ members of the shape coexisting structures observed in the even-even Pt isotopes do not provide as clear an indication of which band is the more spherical as do the corresponding levels in the even-even Hg isotopes. Evidence from... 

Recently Heyde et al. have reviewed the experimental evidence for shape coexistence in odd A nuclei and the theoretical approaches which are made to describe the experimental data [HEY83]. Also in several even mass nuclei there is evidence for shape coexistence. A nice example are the rotational bands on JTT=0+ intruder states in the even mass Sn isotopes [BR079]. 

A brief survey is given of the technique and its limiting parameters. Recent results on moments of proton rich iodine isotopes show shape coexistence and the presence of the gg/2 [404] intruder orbital for A > 118. 

In fact, the first information on phase transitions and shape coexistence was obtained by optical spectroscopy In 1949 Brix and Kopfermann [BRI49] found a... 

Ellipsometry Spectroscopic ellipsometry Imaging ellipsometry Adsorbed amounts/coverages phase transitions thickness and refractive indices. Identification of interfacial molecules. Domain formation eind shape (coexisting phases) internal structure of condensed phases resolution O (1 gm). For interpretation in terms of molecular structure model profiles across the Interface are needed. Problems mono-layer anisotropy, and different profiles may match the experimental data additional (independent) information required. 

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