HfF+ as a candidate to search for the nuclear weak quadrupole moment

Abstract

Nuclei with a quadrupole deformation such as 177 Hf have enhanced weak quadrupole moment which induces the tensor weak electron-nucleus interaction in atoms and molecules. Corresponding parity non-conserving (PNC) effect is strongly enhanced in the 3 ∆1 electronic state of the 177 HfF + cation which has very close opposite parity levels mixed by this tensor interaction. In the present paper we perform relativistic many-body calculations of this PNC effect. It is shown that the tensor weak interaction induced by the weak quadrupole moment gives the dominating contribution to the PNC effects in 177 HfF + which significantly exceeds contributions of the vector anapole moment and the scalar weak charge. The anapole and the weak charge can contribute due to the nonadiabatic mechanism proposed here. Therefore, corresponding experiment will allow one to separate the tensor weak PNC effect from the other PNC effects and to measure the quadrupole moment of the neutron distribution which gives the dominating contribution to the weak quadrupole moment.

Effect of the neutron quadrupole distribution in the TaO+ cation

“…Taking the nuclear quadrupole moment of Ta to be Q p = 3.17 b [19] and tak- ing into account the fact that for deformed nuclei Q n ≈ (N/Z)Q p [11], we estimate the value of W q Q T W ≈ 5 mHz. By the order of magnitude this value is close to that found for the HfF + [20] for the metastable excited 3 ∆ 1 state.…”

“…One can note, that in principle other PNC effects such as the nuclear anapole moment and nuclear weak charge can contribute to the considered amplitude through the nonadiabatic effects. Our previous study of HfF + [20] showed that such contributions are one to two orders of magnitude less than the effect induced by the tensor weak interaction. We are going to explore such effects in TaO + together with possible new physics contributions in future.…”

“…In the present paper we are interested in the following PNC matrix element for the TaO + cation [20]:…”

Nuclear spin-dependent parity-violating effects in light polyatomic molecules

“…Measurements of these moments will allow the first determination of the quadrupole moments of the neutron distribution in nuclei and provide a test of the theory of nuclear forces with applications to nuclei and neutron stars [39][40][41]. As with other NSD-PV effects, the effect of the nuclear weak quadruple moment is expected to be enhanced in certain systems [42].…”

Diagonal and off-diagonal hyperfine structure matrix elements in KCs within the relativistic Fock space coupled cluster theory

“…Accurate theoretical predictions of properties of the ground and excited states of few-atomic molecules are of crucial importance for preparation and interpretation of different fundamental physical experiments such as lasersynthesis of diatomics [1,2], laser cooling of diatomic and polyatomic molecules, experiments aimed at the search for the fundamental symmetry violations effects such as the electron electric dipole moment, etc. In particular, both diagonal and off-diagonal matrix elements of magnetic dipole hyperfine structure (HFS) and other operators, strongly localized in vicinities of atomic nuclei and sometimes referred to as core property operators, are required for the accurate treatment of non-adiabatic effects [3,4], parity non-conserving amplitudes [5] and some other transition properties in molecules. In this regard, magnetic dipole hyperfine structure calculations are of particular interest since they are conventionally used as a probe of the accuracy of theoretical predictions.…”