Search for a permanent electric-dipole moment using atomic indium

Abstract

We propose indium (In) as a possible candidate for observing the permanent electric dipole moment (EDM) arising from violations of parity (P ) and time-reversal (T ) symmetries. This atom has been laser cooled and therefore the measurement of its EDM has the potential of improving on the current best EDM limit for a paramagnetic atom, which comes from thallium. We report the results of our calculations of the EDM enhancement factor due to the electron EDM and the ratio of the atomic EDM to the electron-nucleus scalar-pseudoscalar (S-PS) interaction coupling constant in In within the framework of the relativistic coupled cluster theory. It might be possible to get new limits for the electron EDM and the S-PS CP -violating coupling constant by combining the results of our calculations with the measured value of the EDM of In when it is available. These limits could have important implications for the standard model (SM) of particle physics.It is now widely recognized that atomic electric dipole moments (EDMs) arising from violations of parity (P ) and time-reversal (T ) symmetries can provide important information about new physics beyond the standard model (SM) [1,2].The dominant sources of the EDM of a paramagnetic atom are the EDM of an electron and the scalar-pseudoscalar (S-PS) interaction between the electron and the nucleus which violates P as well as T symmetries [4]. Atomic EDMs due to the electron EDM and the S-PS electron-nucleus interaction can shed light on CP violation in the leptonic and semileptonic sectors [1,5]. The origin of both of these kinds of CP violations is not well understood.The best limit on the EDM of a paramagnetic atom currently comes from thallium (Tl) [6][7][8][9]. A new generation of EDM experiments on the alkali-metal atoms like rubidium [10], caesium [10][11][12], and francium [13] and based on the techniques of laser cooling and trapping is currently underway. These experiments have, in principle, the advantages of both the beam and the cell experiments [14]. In particular, it is possible to apply large electric fields and the coherence times are long in these experiments [14]. The projected precision of the current alkali-metal EDM experiments are about two orders of magnitude better than that of the Tl experiment [10][11][12]. Indium (In), which is homologous to Tl, appears to be an attractive candidate for the search of a permanent EDM for essentially two reasons: First, this atom has been laser cooled [15] and, second, the EDM enhancement factor due to the electron EDM and the ratio of the atomic EDM to the S-PS coupling constant can be calculated more accurately than that of Tl due to its relatively smaller size. To demonstrate this second point more elaborately, we carry out herein ab initio calculations for the corresponding factors due to the EDM of electron and the S-PS electron-nucleus interaction in In and discuss the role of different correlation effects in these properties.

High-Precision Multiphoton Ionization of Accelerated Laser-Ablated Species

“…assumed to be proportional to square-root values of the A hf values of the associated states in the matrix elements [20,21,29,74]. In the indium atom, the A hf values of the 5p 2 P 1=2 and 6-9s 2 S 1=2 states were shown to provide the leading contributions to assess the accuracy of these Hamiltonians [20].…”

“…Theoretical predictions for these states in 115 In were reported in Ref. [20] using the CCSD method with the DC Hamiltonian and considering Gaussian-type orbitals (GTOs). The present theoretical calculations differ slightly in all of the states; however, a significant difference is observed for the 9s 2 S 1=2 state.…”

“…To account for the electron-correlation effects due to the residual Coulomb (and Breit) interactions in the DHF method, a relativistic coupled-cluster (RCC) approach is used to determine the atomic wave functions. In the RCC ansatz, wave functions of an atomic state with a closed core and a valence orbital are expressed as [20,[45][46][47][48][49]…”

“…(ii) The matrix elements of weak-interaction Hamiltonians involved in the electron-nucleon interaction are not experimental observables; quantifying the uncertainty of their theoretical predictions is therefore of paramount importance. Since these matrix elements, as well as the hyperfine interactions, originate from the interaction between the electrons and the atomic nucleus, PNC and EDM calculations are usually adjudged by comparing calculated magnetic dipole hyperfine-structure constants with available measurements [20][21][22]. In this work, we have measured, for the first time, the hfs constants of atomic states in In that are relevant in these studies.…”

“…We have chosen atomic indium (In) to illustrate the impact of our findings in multidisciplinary research, as it exhibits distinct properties that are of interest in nuclear structure, atomic physics, and studies of fundamental symmetries. (i) It has been proposed as a candidate for electric dipole moment (EDM) measurements [20]. Furthermore, its properties constitute a testing ground for atomic-physics calculations directly applicable to other elements of interest in fundamental-physics research, e.g., thallium (Tl), rubidium (Rb), and cesium (Cs) [21][22][23][24][25].…”