W. Satula - Academia.edu (original) (raw)

Papers by W. Satula

Physical Review C, 2007

ABSTRACT Three different rotational bands have been observed to high spin in 75Rb using Gammasphe... more ABSTRACT Three different rotational bands have been observed to high spin in 75Rb using Gammasphere. The structures are similar, but not identical to those found in the neighboring Tz=1/2 nucleus 73Kr. Conventional total Routhian surface (TRS) calculations with T=1 pairing are able to reproduce the rotational bands in 75Rb with extreme accuracy, but they completely fail in reproducing the spectra and decay pattern of the negative parity bands in 73Kr. Simple qualitative arguments are put forward to show that the decay pattern observed in the negative parity bands in 73Kr can be accounted for by means of T=0 pair correlations. To further corroborate this scenario, deformation, and pairing self-consistent TRS calculations, including schematic T=1 and T=0 pairing, are performed for the first time indicating the onset of dynamical T=0 pair-correlations at high angular momenta.

Physical Review Letters, 1996

Quadrupole and hexadecapole moments of superdeformed bands in the A∼150 mass region have been ana... more Quadrupole and hexadecapole moments of superdeformed bands in the A∼150 mass region have been analyzed in the cranking Skyrme-Hartree-Fock model. It is demonstrated that, independently of the intrinsic configuration and of the proton and neutron numbers, the charge moments calculated with respect to the doubly-magic superdeformed core of 152 Dy can be expressed very precisely in terms of independent contributions from the individual hole and particle orbitals. This result, together with earlier studies of the moments of inertia distributions, suggests that many features of the superdeformed bands in the A∼150 mass region can be very well understood in terms of an almost undisturbed single-particle motion.

Physics Letters B, 1997

A cranked mean-field model with two-body T=1 and T=0 pairing interactions is presented. Approxima... more A cranked mean-field model with two-body T=1 and T=0 pairing interactions is presented. Approximate projection onto good particle-number is enforced via an extended Lipkin-Nogami scheme. Our calculations suggest the simultaneous presence of both T=0 and T=1 pairing modes in N=Z nuclei. The transitions between different pairing phases are discussed as a function of neutron/proton excess, T z , and rotational frequency,hω. The additional binding energy due to the T=0 np-pairing correlations, is suggested as a possible microscopic explanation of the Wigner energy term in even-even nuclei.

Physics Letters B, 2006

The physical origin of the nuclear symmetry energy is studied within the relativistic mean field ... more The physical origin of the nuclear symmetry energy is studied within the relativistic mean field (RMF) theory. Based on the nuclear binding energies calculated with and without mean isovector potential for several isobaric chains we confirm earlier Skyrme-Hartree-Fock result that the nuclear symmetry energy strength depends on the mean level spacing ε(A) and an effective mean isovector potential strength κ(A). A detailed analysis of the isospin dependence of the two components contributing to the nuclear symmetry energy reveals a quadratic dependence due to the meanisoscalar potential, ∼ ε T 2 , and, completely unexpectedly, the presence of a strong linear component ∼ κ T (T + 1 + ε/κ) in the isovector potential. The latter generates a nuclear symmetry energy in RMF theory that is proportional to E sym ∼ T (T + 1) at variance to the non-relativistic calculation. The origin of the linear term in RMF theory needs to be further explored.

Physical Review Letters, 1999

Structures of the medium-to high-spin states in the doubly magic nucleus 56 Ni have been investig... more Structures of the medium-to high-spin states in the doubly magic nucleus 56 Ni have been investigated using the reaction 28 Si͑ 36 Ar, 2a͒ and the gray spectrometer Gammasphere in conjunction with the 4p charged-particle detector array Microball. Two well-deformed rotational bands have been identified. There is evidence that one of the bands, which is identical to a sequence in the odd-odd neighbor 58 Cu, partially decays via proton emission into the ground state of 55 Co. Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data. [S0031-9007(99)09147-4]

Physica Scripta, 1995

... for the first time. obtained a satisfactory agreement for most of the structures. 3.1. Intrrr... more ... for the first time. obtained a satisfactory agreement for most of the structures. 3.1. Intrrrdrr hrrnds in I"'. lo', ' lo . ' ' I Cd nuclei The formation of intruder bands for Cd nuclei is suggested to be associated with 2p-4h excitations across the Z = 50 shell gap [39]. ...

Physics Letters B, 1997

Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinui... more Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinuity at N =Z. This cusp (Wigner energy), reflecting an additional binding in nuclei with neutrons and protons occupying the same shell model orbitals, is usually attributed to neutron-proton pairing correlations. A method is developed to extract the Wigner term from experimental data. Both empirical arguments and shell-model calculations suggest that the Wigner term can be traced back to the isospin T =0 part of nuclear interaction. Our calculations reveal the rather complex mechanism responsible for the nuclear binding around the N =Z line. In particular, we find that the Wigner term cannot be solely explained in terms of correlations between the neutron-proton J=1, T =0 (deuteron-like) pairs.

Soryushiron Kenkyu Electronics, 2007

Systematic calculations of favored signature maximum-spin Imax and unfavored signature Imax − 1 t... more Systematic calculations of favored signature maximum-spin Imax and unfavored signature Imax − 1 terminating states for [f n 7/2 ] and [d −1 3/2 f n+1 7/2 ] configurations (n denotes number of valence particles) in A∼44 mass region are presented. Following the result of Zduńczuk et al., Phys. Rev. C71 (2005) 024305 the calculations are performed using Skyrme energy density functional with empirical Landau parameters and slightly reduced spin-orbit strength. The aim is to identify and phenomenologically restore rotational symmetry broken by the Skyrme-Hartree-Fock solutions. In particular, it is shown that correlation energy due to symmetry restoration is absolutely crucial in order to reproduce energy splitting E(Imax) − E(Imax − 1) in [f n 7/2 ] configurations but is relatively less important for [d −1 3/2 f n+1 7/2 ] configurations.

AIP Conference Proceedings, 1992

A brief reminder is given of the evidence for the existence of octupole correlations in the super... more A brief reminder is given of the evidence for the existence of octupole correlations in the superdeformed shape of 193Hg. It is pointed out that comparison of the data on the superdeformed bands in 19Hg with Cranked Shell Model calculations gives firm assignments to the signatures and parities of these bands. The spin assignments obtained are in agreement with the

International Journal of Modern Physics E, 2009

We report on the development of a new theoretical tool that allows for isospin projection of Slat... more We report on the development of a new theoretical tool that allows for isospin projection of Slater determinants and we present its first applications. In particular, we determine the isospin mixing in ground states of N = Z nuclei and discuss its dependence on the size of the harmonic-oscillator basis used in the calculations. We also discuss the unphysical contribution to the isospin mixing caused by the spurious isospin-symmetry breaking inherent to the mean-field approach. We show that these contributions may be as large as 30% of the value of the isospin-mixing parameter.

The Nuclear Many-Body Problem 2001, 2002

Nuclear pairing is an intrinsic phenomenon predominantly related to the attractiveness of the sho... more Nuclear pairing is an intrinsic phenomenon predominantly related to the attractiveness of the short-range part of the effective nuclear interaction at the Fermi energy. Since in most nuclei proton and neutron Fermi energies lie far apart, in most applications it is enough to consider only isovector pp—and nn— (t = 1,t z = ± 1) correlations. However, both charge independence of the nuclear force as well as stronger, on the average, attractivness of the isoscalar (t=0) interaction do suggest that proton-neutron (pn—)type pairing may be of importance in N~Z nuclei and indeed standard mean-field calculations seem to systematically underbind N=Z nuclei. Interestingly, the isoscalar (t=0) pn—pairing can provide locally [i.e. for N~Z] an extra binding -the so called Wigner energy -offering a simple and intuitive microscopic explanation to this problem [1, 2].

The spin-orbit (SO) interaction, emerging naturally from the Relativistic Mean Field (RMF) theory... more The spin-orbit (SO) interaction, emerging naturally from the Relativistic Mean Field (RMF) theory is examined critically in the light of the recently measured excitation energy differences between the terminating states built on two different configurations for nuclei belonging to the lower pf shell. The calculations are carried out using the cranked RMF framework. To further probe the iso-vector dependence of the spin-orbit potential, the energy spacing between the g_{7/2} and h_{11/2} states in the Sb-chain is compared to experiment. It is found that the calculation at the quantitative level deviates strongly from the experiment. In particular the balance of the iso-scalar and iso-vector strengths of the effective one body SO potential indicates that additional terms like tensor couplings may be needed to account for the experimental data.

Physical Review Letters, 2007

Calculations of nuclear masses, using nuclear density functional theory, are presented for evenev... more Calculations of nuclear masses, using nuclear density functional theory, are presented for eveneven nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.

Physical Review Letters, 2001

Excitation energies of the T =1 states in even-even as well as T =0 and T =1 states in odd-odd N ... more Excitation energies of the T =1 states in even-even as well as T =0 and T =1 states in odd-odd N =Z nuclei are calculated within the mean-field approach. It is shown that the underlying structure of these states can be determined in a consistent manner only when both isoscalar and isovector pairing collectivity as well as isospin projection, treated within the iso-cranking approximation, are taken into account. In particular, in odd-odd N =Z nuclei, the interplay between quasiparticle excitations (relevant for the case of T =0 states) and iso-rotations (relevant for the case of T =1 states) explains the near-degeneracy of these fundamental excitations.

Physical Review Letters, 2002

The latest generation gamma-ray detection system, GAMMASPHERE, coupled with the Microball charged... more The latest generation gamma-ray detection system, GAMMASPHERE, coupled with the Microball charged-particle detector, has made possible a new class of nuclear lifetime measurement. For the first time differential lifetime measurements free from common systematic errors for over 15 different nuclei ( >30 rotational bands in various isotopes of Ce, Pr, Nd, Pm, and Sm) have been extracted at high spin within a single experiment. This comprehensive study establishes the effective single-particle transition quadrupole moments in the A approximately 135 light rare-earth region. Detailed comparisons are made with theoretical calculations using the self-consistent cranked mean-field theory which convincingly demonstrates the validity of the additivity of single-particle quadrupole moments in this mass region.

Nuclear Physics A, 1990

Three superdeformed (SD) bands have been observed in 194Hg and four (or five?) SD bands in ~93Hg ... more Three superdeformed (SD) bands have been observed in 194Hg and four (or five?) SD bands in ~93Hg using the ~5°Nd + 48Ca reaction. All bands excelot for two in ~93Hg show a steady increase in dynamical moment of inertia 3(2rwith rotational frequency. The two exceptional bands form a classical pair of strongly interacting bands. It is suggested that the strong interaction between the bands is caused by a softness to octupole deformation. Evidence is found for the existence of dipole transitions connecting bands of opposite signature in 193Hg. The strengths of these transitions suggest that they are probably E1 supporting the importance of the role of octupole vibrations. These data suggest the wider importance of octupole softness in enhancing E1 transitions in the SD feeding and decay mechanisms. The spectroscopy of the observed SD bands in 193'4Hg are discussed in detail and attention is drawn to the "identical" energies of ,/-rays in these isotopes with those in lighter isotopes. The similarities in bands relate to the neutron sub-shell closure for SD nuclei at N=112.

Nuclear Physics A, 1993

... 5.7.7. Example: An z proton bands in Sb nuclei Rotational bands have been observed quite some... more ... 5.7.7. Example: An z proton bands in Sb nuclei Rotational bands have been observed quite some time ago in the Sn isotopes [34,35] and can be associated with a twoparticletwohole excitation across the Z = 50 shell gap [34,36]. ...

Nuclear Physics A, 2000

A mean-field model with a generalized pairing interaction that accounts for neutron-proton pairin... more A mean-field model with a generalized pairing interaction that accounts for neutron-proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin-Nogami projection technique was extended to encompass the case of non-separable proton-neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows for mixing of different pairing phases but, simultanously, acts destructively on the proton-neutron correlations. The basic implications of proton-neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in 88 Ru are given.

Physical Review C, 2007

ABSTRACT Three different rotational bands have been observed to high spin in 75Rb using Gammasphe... more ABSTRACT Three different rotational bands have been observed to high spin in 75Rb using Gammasphere. The structures are similar, but not identical to those found in the neighboring Tz=1/2 nucleus 73Kr. Conventional total Routhian surface (TRS) calculations with T=1 pairing are able to reproduce the rotational bands in 75Rb with extreme accuracy, but they completely fail in reproducing the spectra and decay pattern of the negative parity bands in 73Kr. Simple qualitative arguments are put forward to show that the decay pattern observed in the negative parity bands in 73Kr can be accounted for by means of T=0 pair correlations. To further corroborate this scenario, deformation, and pairing self-consistent TRS calculations, including schematic T=1 and T=0 pairing, are performed for the first time indicating the onset of dynamical T=0 pair-correlations at high angular momenta.

Physical Review Letters, 1996

Quadrupole and hexadecapole moments of superdeformed bands in the A∼150 mass region have been ana... more Quadrupole and hexadecapole moments of superdeformed bands in the A∼150 mass region have been analyzed in the cranking Skyrme-Hartree-Fock model. It is demonstrated that, independently of the intrinsic configuration and of the proton and neutron numbers, the charge moments calculated with respect to the doubly-magic superdeformed core of 152 Dy can be expressed very precisely in terms of independent contributions from the individual hole and particle orbitals. This result, together with earlier studies of the moments of inertia distributions, suggests that many features of the superdeformed bands in the A∼150 mass region can be very well understood in terms of an almost undisturbed single-particle motion.

Physics Letters B, 1997

A cranked mean-field model with two-body T=1 and T=0 pairing interactions is presented. Approxima... more A cranked mean-field model with two-body T=1 and T=0 pairing interactions is presented. Approximate projection onto good particle-number is enforced via an extended Lipkin-Nogami scheme. Our calculations suggest the simultaneous presence of both T=0 and T=1 pairing modes in N=Z nuclei. The transitions between different pairing phases are discussed as a function of neutron/proton excess, T z , and rotational frequency,hω. The additional binding energy due to the T=0 np-pairing correlations, is suggested as a possible microscopic explanation of the Wigner energy term in even-even nuclei.

Physics Letters B, 2006

The physical origin of the nuclear symmetry energy is studied within the relativistic mean field ... more The physical origin of the nuclear symmetry energy is studied within the relativistic mean field (RMF) theory. Based on the nuclear binding energies calculated with and without mean isovector potential for several isobaric chains we confirm earlier Skyrme-Hartree-Fock result that the nuclear symmetry energy strength depends on the mean level spacing ε(A) and an effective mean isovector potential strength κ(A). A detailed analysis of the isospin dependence of the two components contributing to the nuclear symmetry energy reveals a quadratic dependence due to the meanisoscalar potential, ∼ ε T 2 , and, completely unexpectedly, the presence of a strong linear component ∼ κ T (T + 1 + ε/κ) in the isovector potential. The latter generates a nuclear symmetry energy in RMF theory that is proportional to E sym ∼ T (T + 1) at variance to the non-relativistic calculation. The origin of the linear term in RMF theory needs to be further explored.

Physical Review Letters, 1999

Structures of the medium-to high-spin states in the doubly magic nucleus 56 Ni have been investig... more Structures of the medium-to high-spin states in the doubly magic nucleus 56 Ni have been investigated using the reaction 28 Si͑ 36 Ar, 2a͒ and the gray spectrometer Gammasphere in conjunction with the 4p charged-particle detector array Microball. Two well-deformed rotational bands have been identified. There is evidence that one of the bands, which is identical to a sequence in the odd-odd neighbor 58 Cu, partially decays via proton emission into the ground state of 55 Co. Predictions of extensive large-scale shell-model and cranked Hartree-Fock and Hartree-Fock-Bogolyubov calculations are compared with the experimental data. [S0031-9007(99)09147-4]

Physica Scripta, 1995

... for the first time. obtained a satisfactory agreement for most of the structures. 3.1. Intrrr... more ... for the first time. obtained a satisfactory agreement for most of the structures. 3.1. Intrrrdrr hrrnds in I"'. lo', ' lo . ' ' I Cd nuclei The formation of intruder bands for Cd nuclei is suggested to be associated with 2p-4h excitations across the Z = 50 shell gap [39]. ...

Physics Letters B, 1997

Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinui... more Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinuity at N =Z. This cusp (Wigner energy), reflecting an additional binding in nuclei with neutrons and protons occupying the same shell model orbitals, is usually attributed to neutron-proton pairing correlations. A method is developed to extract the Wigner term from experimental data. Both empirical arguments and shell-model calculations suggest that the Wigner term can be traced back to the isospin T =0 part of nuclear interaction. Our calculations reveal the rather complex mechanism responsible for the nuclear binding around the N =Z line. In particular, we find that the Wigner term cannot be solely explained in terms of correlations between the neutron-proton J=1, T =0 (deuteron-like) pairs.

Soryushiron Kenkyu Electronics, 2007

Systematic calculations of favored signature maximum-spin Imax and unfavored signature Imax − 1 t... more Systematic calculations of favored signature maximum-spin Imax and unfavored signature Imax − 1 terminating states for [f n 7/2 ] and [d −1 3/2 f n+1 7/2 ] configurations (n denotes number of valence particles) in A∼44 mass region are presented. Following the result of Zduńczuk et al., Phys. Rev. C71 (2005) 024305 the calculations are performed using Skyrme energy density functional with empirical Landau parameters and slightly reduced spin-orbit strength. The aim is to identify and phenomenologically restore rotational symmetry broken by the Skyrme-Hartree-Fock solutions. In particular, it is shown that correlation energy due to symmetry restoration is absolutely crucial in order to reproduce energy splitting E(Imax) − E(Imax − 1) in [f n 7/2 ] configurations but is relatively less important for [d −1 3/2 f n+1 7/2 ] configurations.

AIP Conference Proceedings, 1992

A brief reminder is given of the evidence for the existence of octupole correlations in the super... more A brief reminder is given of the evidence for the existence of octupole correlations in the superdeformed shape of 193Hg. It is pointed out that comparison of the data on the superdeformed bands in 19Hg with Cranked Shell Model calculations gives firm assignments to the signatures and parities of these bands. The spin assignments obtained are in agreement with the

International Journal of Modern Physics E, 2009

We report on the development of a new theoretical tool that allows for isospin projection of Slat... more We report on the development of a new theoretical tool that allows for isospin projection of Slater determinants and we present its first applications. In particular, we determine the isospin mixing in ground states of N = Z nuclei and discuss its dependence on the size of the harmonic-oscillator basis used in the calculations. We also discuss the unphysical contribution to the isospin mixing caused by the spurious isospin-symmetry breaking inherent to the mean-field approach. We show that these contributions may be as large as 30% of the value of the isospin-mixing parameter.

The Nuclear Many-Body Problem 2001, 2002

Nuclear pairing is an intrinsic phenomenon predominantly related to the attractiveness of the sho... more Nuclear pairing is an intrinsic phenomenon predominantly related to the attractiveness of the short-range part of the effective nuclear interaction at the Fermi energy. Since in most nuclei proton and neutron Fermi energies lie far apart, in most applications it is enough to consider only isovector pp—and nn— (t = 1,t z = ± 1) correlations. However, both charge independence of the nuclear force as well as stronger, on the average, attractivness of the isoscalar (t=0) interaction do suggest that proton-neutron (pn—)type pairing may be of importance in N~Z nuclei and indeed standard mean-field calculations seem to systematically underbind N=Z nuclei. Interestingly, the isoscalar (t=0) pn—pairing can provide locally [i.e. for N~Z] an extra binding -the so called Wigner energy -offering a simple and intuitive microscopic explanation to this problem [1, 2].

The spin-orbit (SO) interaction, emerging naturally from the Relativistic Mean Field (RMF) theory... more The spin-orbit (SO) interaction, emerging naturally from the Relativistic Mean Field (RMF) theory is examined critically in the light of the recently measured excitation energy differences between the terminating states built on two different configurations for nuclei belonging to the lower pf shell. The calculations are carried out using the cranked RMF framework. To further probe the iso-vector dependence of the spin-orbit potential, the energy spacing between the g_{7/2} and h_{11/2} states in the Sb-chain is compared to experiment. It is found that the calculation at the quantitative level deviates strongly from the experiment. In particular the balance of the iso-scalar and iso-vector strengths of the effective one body SO potential indicates that additional terms like tensor couplings may be needed to account for the experimental data.

Physical Review Letters, 2007

Calculations of nuclear masses, using nuclear density functional theory, are presented for evenev... more Calculations of nuclear masses, using nuclear density functional theory, are presented for eveneven nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.

Physical Review Letters, 2001

Excitation energies of the T =1 states in even-even as well as T =0 and T =1 states in odd-odd N ... more Excitation energies of the T =1 states in even-even as well as T =0 and T =1 states in odd-odd N =Z nuclei are calculated within the mean-field approach. It is shown that the underlying structure of these states can be determined in a consistent manner only when both isoscalar and isovector pairing collectivity as well as isospin projection, treated within the iso-cranking approximation, are taken into account. In particular, in odd-odd N =Z nuclei, the interplay between quasiparticle excitations (relevant for the case of T =0 states) and iso-rotations (relevant for the case of T =1 states) explains the near-degeneracy of these fundamental excitations.

Physical Review Letters, 2002

The latest generation gamma-ray detection system, GAMMASPHERE, coupled with the Microball charged... more The latest generation gamma-ray detection system, GAMMASPHERE, coupled with the Microball charged-particle detector, has made possible a new class of nuclear lifetime measurement. For the first time differential lifetime measurements free from common systematic errors for over 15 different nuclei ( >30 rotational bands in various isotopes of Ce, Pr, Nd, Pm, and Sm) have been extracted at high spin within a single experiment. This comprehensive study establishes the effective single-particle transition quadrupole moments in the A approximately 135 light rare-earth region. Detailed comparisons are made with theoretical calculations using the self-consistent cranked mean-field theory which convincingly demonstrates the validity of the additivity of single-particle quadrupole moments in this mass region.

Nuclear Physics A, 1990

Three superdeformed (SD) bands have been observed in 194Hg and four (or five?) SD bands in ~93Hg ... more Three superdeformed (SD) bands have been observed in 194Hg and four (or five?) SD bands in ~93Hg using the ~5°Nd + 48Ca reaction. All bands excelot for two in ~93Hg show a steady increase in dynamical moment of inertia 3(2rwith rotational frequency. The two exceptional bands form a classical pair of strongly interacting bands. It is suggested that the strong interaction between the bands is caused by a softness to octupole deformation. Evidence is found for the existence of dipole transitions connecting bands of opposite signature in 193Hg. The strengths of these transitions suggest that they are probably E1 supporting the importance of the role of octupole vibrations. These data suggest the wider importance of octupole softness in enhancing E1 transitions in the SD feeding and decay mechanisms. The spectroscopy of the observed SD bands in 193'4Hg are discussed in detail and attention is drawn to the "identical" energies of ,/-rays in these isotopes with those in lighter isotopes. The similarities in bands relate to the neutron sub-shell closure for SD nuclei at N=112.

Nuclear Physics A, 1993

... 5.7.7. Example: An z proton bands in Sb nuclei Rotational bands have been observed quite some... more ... 5.7.7. Example: An z proton bands in Sb nuclei Rotational bands have been observed quite some time ago in the Sn isotopes [34,35] and can be associated with a twoparticletwohole excitation across the Z = 50 shell gap [34,36]. ...

Nuclear Physics A, 2000

A mean-field model with a generalized pairing interaction that accounts for neutron-proton pairin... more A mean-field model with a generalized pairing interaction that accounts for neutron-proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin-Nogami projection technique was extended to encompass the case of non-separable proton-neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows for mixing of different pairing phases but, simultanously, acts destructively on the proton-neutron correlations. The basic implications of proton-neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in 88 Ru are given.