Large Permanent Electric Dipole Moment Research Articles

Photoassociation spectra of cesium 31D<sub>5/2</sub>+6S<sub>1/2</sub>(<i>F</i> = 4) ultra-long range Rydberg molecules

In this paper, we conduct the experiment and simulation on 31D<sub>5/2</sub>+6S<sub>1/2</sub>(<i>F</i> = 4) Cs<sub>2</sub> ULRMs. These molecules are prepared by employing a two-photon photoassociation scheme. Two distinct ultralong-range Rydberg molecular signals are observed at the detuning −162.8MHz and −66.6MHz of 31D<sub>5/2</sub> atomic resonant line, which are bound by the pure triplet potential and mixed singlet-triplet potential, respectively. We use the model of scattering interaction between the Rydberg electron and ground-state atom to perform the simulation. The molecular potential-energy curves are obtained by solving the Hamiltonian on a grid of intermolecular distances <i>R</i>. The calculations of the binding energy of pure triplet and mixed singlet-triplet <i>v</i> = 0 vibrational states are compared with the experimental measurements. The calculated and measured values of the binding energy are in good agreement. The <i>s</i>-wave pure triplet and singlet zero-energy scattering length are obtained to be<inline-formula><tex-math id="M3">\begin{document}$ {a}_{{\rm{s}}}^{{\rm{T}}}\left(\text{0}\right)=-\text{19.16}{a}_{0} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230520_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230520_M3.png"/></alternatives></inline-formula> and<inline-formula><tex-math id="M4">\begin{document}$ {a}_{{\rm{s}}}^{{\rm{S}}}\left(0\right)=-\text{1.92}{a}_{0} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230520_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="14-20230520_M4.png"/></alternatives></inline-formula>, respectively. This kind of molecule with large size, abundant vibrational states and large permanent electric dipole moment is an excellent candidate for studying low-energy collision dynamics. The study of these molecules will further deepen and enrich the understanding of the special binding mechanism and exotic properties of the ULRMs.

Interaction potentials, electric moments, polarizabilities, and chemical reactions of YbCu, YbAg, and YbAu molecules

Ultracold YbAg molecules have been recently proposed as promising candidates for electron electric dipole moment searches Verma et al (2020 Phys. Rev. Lett. 125 153201). Here, we calculate potential energy curves, permanent electric dipole and quadrupole moments, and static electric dipole polarizabilities for the YbCu, YbAg, and YbAu molecules in their ground electronic states. We use the coupled cluster method restricted to single, double, and noniterative triple excitations with large Gaussian basis sets, while the scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. We find that the studied molecules are relatively strongly bound with the well depths of 5708 cm−1, 5253 cm−1, and 13349 cm−1 and equilibrium distances of 5.50 bohr, 5.79 bohr, and 5.55 bohr for YbCu, YbAg, and YbAu, respectively. They have large permanent electric dipole moments of 3.2D, 3.3D, and 5.3D at equilibrium distances, respectively. We also calculate equilibrium geometries and energies of corresponding trimers. The studied molecules are chemically reactive unless they are segregated in an optical lattice or shielded with external fields. The investigated molecules may find application in ultracold controlled chemistry, dipolar many-body physics, or precision measurement experiments.

Highly polar molecules consisting of a copper or silver atom interacting with an alkali-metal or alkaline-earth-metal atom

We theoretically investigate the properties of highly polar diatomic molecules containing $^2S$-state transition-metal atoms. We calculate potential energy curves, permanent electric dipole moments, spectroscopic constants, and leading long-range dispersion-interaction coefficients for molecules consisting of either a Cu or Ag atom interacting with an alkali-metal (Li, Na, K, Rb, Cs, Fr) or alkaline-earth-metal (Be, Mg, Ca, Sr, Ba, Ra) atom. We use ab initio electronic structure methods, such as the coupled cluster and configuration interaction ones, with large Gaussian basis sets and small-core relativistic energy-consistent pseudopotentials. We predict that the studied molecules in the ground electronic state are strongly bound with highly polarized covalent or ionic bonds resulting in very large permanent electric dipole moments. We find that highly excited vibrational levels have maximal electric dipole moments, e.g., exceeding 13$\,$debye for CsAg and 6$\,$debye for BaAg. Results for Cu$_2$, Ag$_2$, and CuAg are also reported. The studied molecules may find application in ultracold dipolar many-body physics, controlled chemistry, or precision measurement experiments.

Merits of heavy-heavy diatomic molecules for electron electric-dipole-moment searches

The electric dipole moment of the electron (eEDM) and the Scalar-PseudoScalar (S-PS) interaction are probes of new physics beyond the standard model of elementary particles, but experiments to observe them using atoms and molecules are still in progress. Molecules that have a large effective electric field (Eeff), S-PS coefficient (Ws), and permanent electric dipole moment (PDM) are in principle favorable candidates for such experiments, and hence, it is necessary to analyze these properties. In this work, we calculate Eeff, Ws, and PDM for Ra systems; RaF, RaX (X = Cl, Br, I, and At) and RaY (Y = Cu, Ag, and Au) using the Dirac-Fock and the relativistic coupled-cluster methods. We find that RaX and RaY have larger Eeff and Ws,Ra than RaF. We explain this finding by taking into consideration the large s-p mixing for RaX and RaY, similar to what we had done in our previous work using hydrides and fluorides (A. Sunaga et al., Phys. Rev. A 95, 012502 (2017)). We also discuss the suitability of RaX and RaY molecules for eEDM experiments from the viewpoint of their large PDM and small polarizing electric field (Epol).

RaH as a potential candidate for electron electric-dipole-moment searches

Diatomic polar molecules have been the focus of research in the recent past as candidates for electron electric dipole moment (eEDM), de, measurements. In the present work, we focus on RaH molecule and have calculated three of its properties (in the X2Σ+ state) the effective electric field (Eeff), the scalar-pseudoscalar (S-PS) interaction coefficient (Ws,A), and permanent electric dipole moment (PDM) that play crucial roles in probing fundamental symmetry violations. The calculations were based on the relativistic coupled-cluster singles and doubles (RCCSD) frame work. Our results for Eeff, Ws,A, and PDM are 80.31 GV/cm, 216.82 kHz, and 4.44 D respectively. In addition to possessing high magnitudes of Eeff and Ws,A, RaH also has a large PDM, which is a highly desirable criterion for eEDM experiments. The analysis of our results clearly indicates the spectacular role of electron correlation in enhancing their magnitudes ≈16% for PDM and ≈31% for Eeff and Ws,A. The ratio of Eeff to Ws,A for RaH is 89.56×1018e−1 cm−1. Based on our results and other experimental considerations, we propose RaH as a future candidate for experiments in this field.

Prospects for the formation of ultracold polar ground state KCs molecules via an optical process

Heteronuclear alkali-metal dimers represent the class of molecules of choice for creating samples of ultracold molecules exhibiting an intrinsic large permanent electric dipole moment. Among them, the KCs molecule, with a permanent dipole moment of 1.92 Debye still remains to be observed in ultracold conditions. Based on spectroscopic studies available in the literature completed by accurate quantum chemistry calculations, we propose several optical coherent schemes to create ultracold bosonic and fermionic KCs molecules in their absolute rovibrational ground level, starting from a weakly bound level of their electronic ground state manifold. The processes rely on the existence of convenient electronically excited states allowing an efficient stimulated Raman adiabatic transfer of the level population.

How do ultralong-range homonuclear Rydberg molecules get their permanent dipole moments?

Cold and ultracold Rydberg atoms are in considerable vogue for their ability to creating strong interactions, stemming from their exaggerated and readily tunable properties. Ultralong-range Rydberg molecules have been predicted to form from the interaction of ultracold Rydberg atoms with ground-state atoms and polar molecules. In this work, we discuss and demonstrate how such molecules, which are homonuclear, form substantially large permanent electric dipole moments. A corollary benefit of such strong hybridisation is the realisation of high angular momentum degenerate Rydberg molecules (so-called trilobite molecules) with standard photoassociation techniques.

Hyperfine molecular Hubbard Hamiltonian

An ultracold gas of heteronuclear alkali-metal dimer molecules with hyperfine structure loaded into a one-dimensional optical lattice is investigated. The hyperfine molecular Hubbard Hamiltonian (HMHH), an effective low-energy lattice Hamiltonian, is derived from first principles. The large permanent electric dipole moment of these molecules gives rise to long-range dipole-dipole forces in a dc electric field and allows for transitions between rotational states in an ac microwave field. Additionally, a strong magnetic field can be used to control the hyperfine degrees of freedom independently of the rotational degrees of freedom. By tuning the angle between the dc electric and magnetic fields and the strength of the ac field, it is possible to control the number of internal states involved in the dynamics as well as the degree of correlation between the spatial and internal degrees of freedom. The HMHH's unique features have direct experimental consequences such as quantum dephasing, tunable complexity, and the dependence of the phase diagram on the molecular state.

Chiral Self-Recognition: Direct Spectroscopic Detection of the Homochiral and Heterochiral Dimers of Propylene Oxide in the Gas Phase

In this report, we describe rotational spectroscopic and high-level ab initio studies of the 1:1 chiral molecular adduct of propylene oxide dimer. The complexes are bound by weak secondary hydrogen bonds, that is, the O(epoxy)...H-C noncovalent interactions. Six homochiral and six heterochiral conformers were predicted to be the most stable configurations where each monomer acts as a proton acceptor and a donor simultaneously, forming two six- or five-membered intermolecular hydrogen-bonded rings. Rotational spectra of six, that is, three homochiral and heterochiral conformer pairs, out of the eight conformers that were predicted to have sufficiently large permanent electric dipole moments were measured and analyzed. The relative conformational stability order and the signs of the chiral recognition energies of the six conformers were determined experimentally and were compared to the ab initio computational results. The experimental observations and the ab initio calculations suggest that the concerted effort of these weak secondary hydrogen bonds can successfully lock the subunits in a particular orientation and that the overall binding strength is comparable to a classic hydrogen bond.

The experiment on the saturation polarization of Rb vapour

A cylindrical capacitor containing rubidium vapour is made. The capacitance of it at different voltages is measured under a certain Rb vapour pressure. The experimental C–V curve shows that the saturation polarization of Rb vapour is easily observed. The experiment further supports the idea that the Rb atom has a large permanent electric dipole moment.

Origin of permanent electric dipole moments in wurtzite nanocrystals

A simple model is presented which explains the origin and magnitude of large permanent electric dipole moments recently observed for CdSe nanorods. It is based on the small crystallographic deviations of the CdSe lattice from the ideal wurtzite structure. The permanent electric dipole moment is found to scale with the volume of the nanocrystal, as observed experimentally.

Comment on ``Permanent Electric Dipole Moment of an RbAtom''

It is stated that the conjecture that thehydrogen-like atoms may have large permanent electric dipole moments isdoubtable. Two kinds of experiments are suggested to check thereliability of the conjecture further.

Permanent Electric Dipole Moment of an Rb Atom

We experimentally determine the conjecture that hydrogen-like atomssuch as Rb and Cs may have large permanent electric dipole moments(EDMs). The saturated Rb vapour fills a cylindrical capacitor inthe experiment. The influence of the vapour dielectric medium oncapacitance is measured with a digital capacitance meter. Supposingthat the measurement influence comes from the permanent EDMs of Rbatoms, from the experimental result we find that the EDM is large,i.e. dRb⩾8.6e×10-9 cm.

Phase behaviors of ammonia/R-125 mixtures

Hydrofluorocarbons (HFCs) are known to have specific intermolecular interactions (hydrogen bonding) as well as large permanent electric dipole moments. The peculiar vapor–liquid equilibria (VLE) behavior (double azeotropes) observed in ammonia/R-125 mixtures led us further to study the phase behaviors of this binary system. The experimental VLE ( PTx) data were measured from 205 to 248 K for six concentrations. Single gaseous phase PTVx properties for four concentrations were measured using a constant volume cell: densities of 100, 102, 146, and 224 kg m −3 at temperature ranges of 333–385 K. The experimental data, combined with the previously reported data, were analyzed with a cubic equation of state, where non-conventional mixing rules were required in order to fit the experimental VLE data satisfactorily. The VLE phase behavior is discussed with ammonia mixtures with other compounds. There are strong evidences that some of HFCs and HCFCs form complexes (or even react) with ammonia. The complex formation and VLE behavior are elusively related to the number of fluorine atoms and the molecular structure. For ammonia/R-125, it is estimated the enthalpy of complex formation is about −10 kJ mol −1, which is in concordance with those for hydrogen-bonding and/or charge-transfer complexes reported in the literature.