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19 pages, 2243 KiB

Open AccessArticle

Theoretical Calculation of Ground and Electronically Excited States of MgRb⁺ and SrRb⁺ Molecular Ions: Electronic Structure and Prospects of Photo-Association

by Mohamed Farjallah, Hela Ladjimi, Wissem Zrafi and Hamid Berriche

Atoms 2025, 13(8), 69; https://doi.org/10.3390/atoms13080069 - 25 Jul 2025

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Abstract

In this work, a comprehensive theoretical investigation is carried out to explore the electronic and spectroscopic properties of selected diatomic molecular ions MgRb⁺ and SrRb⁺. Using high-level ab initio calculations based on a pseudopotential approach, along with large Gaussian basis [...] Read more.

In this work, a comprehensive theoretical investigation is carried out to explore the electronic and spectroscopic properties of selected diatomic molecular ions MgRb⁺ and SrRb⁺. Using high-level ab initio calculations based on a pseudopotential approach, along with large Gaussian basis sets and full valence configuration interaction (FCI), we accurately determine adiabatic potential energy curves, spectroscopic constants, transition dipole moments (TDMs), and permanent electric dipole moments (PDMs). To deepen our understanding of these systems, we calculate radiative lifetimes for vibrational levels in both ground and low-lying excited electronic states. This includes evaluating spontaneous and stimulated emission rates, as well as the effects of blackbody radiation. We also compute Franck–Condon factors and analyze photoassociation processes for both ions. Furthermore, to explore low-energy collisional dynamics, we investigate elastic scattering in the first excited states (2¹Σ⁺) describing the collision between the Ra atom and Mg⁺ or Sr⁺ ions. Our findings provide detailed insights into the theoretical electronic structure of these molecular ions, paving the way for future experimental studies in the field of cold and ultracold molecular ion physics. Full article

(This article belongs to the Section Quantum Chemistry, Computational Chemistry and Molecular Physics)

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18 pages, 287 KiB

Open AccessArticle

Electric Octupole-Dependent Contributions to Optical Binding Energy

by A. Salam

Physics 2024, 6(1), 376-393; https://doi.org/10.3390/physics6010025 - 6 Mar 2024

Viewed by 1196

Abstract

Contributions to the radiation-induced dispersion energy shift between two interacting particles dependent on the electric octupole moment are calculated using a physical picture in which moments induced by applied fluctuating electromagnetic fields are coupled via retarded interaction tensors. The specific potentials evaluated include [...] Read more.

Contributions to the radiation-induced dispersion energy shift between two interacting particles dependent on the electric octupole moment are calculated using a physical picture in which moments induced by applied fluctuating electromagnetic fields are coupled via retarded interaction tensors. The specific potentials evaluated include those found between an electric dipole-polarisable molecule and either a mixed electric dipole–octupole- or purely octupole-polarisable molecule, and those between two mixed electric dipole–octupole-polarisable molecules. Interaction energies are obtained for molecular and pair orientationally averaged situations. Terms dependent on the octupole weight-1 moment may be viewed as higher-order corrections to the leading dipole–dipole interaction energy as also found in energy transfer and dispersion forces. A comprehensive polarisation analysis is carried out for linearly and circularly polarised laser light incident parallel and perpendicular to the inter-particle axis. Contributions to the optical binding energy arising when one of the pair is polar and characterised by either a permanent electric dipole or octupole moment are also evaluated. Neither of these energy shifts survive orientational averaging. Full article

(This article belongs to the Special Issue Matter-Radiation Interactions—In Memory of Professor Francesco Saverio Persico)

11 pages, 333 KiB

Open AccessArticle

Study of He–Mckellar–Wilkens Effect in Noncommutative Space

by Jian Jing, Qing Wang, Zi-Gang Yuan and Shi-Hai Dong

Universe 2023, 9(12), 494; https://doi.org/10.3390/universe9120494 - 27 Nov 2023

Cited by 1 | Viewed by 1615

Abstract

The He–McKellar–Wilkens (HMW) effect in noncommutative space has been explored through two distinct methodologies. One approach treats the neutral particle, which harbors a permanent electric dipole moment, as an unstructured entity, while the other approach considers the neutral particle as a composite system [...] Read more.

The He–McKellar–Wilkens (HMW) effect in noncommutative space has been explored through two distinct methodologies. One approach treats the neutral particle, which harbors a permanent electric dipole moment, as an unstructured entity, while the other approach considers the neutral particle as a composite system consisting of a pair of oppositely charged particles. To preserve gauge symmetry, we apply the Seiberg–Witten map. Surprisingly, both of these approaches converge on the same result. They independently confirm that, up to the first order of the noncommutative parameter (NCP), no corrections are observed in the phase of the HMW effect. Remarkably, these two approaches, although founded on fundamentally different mechanisms, yield identical conclusions. Full article

(This article belongs to the Special Issue Approaches towards Quantum Foundations)

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5 pages, 5675 KiB

Open AccessProceeding Paper

Status of the muEDM Experiment at PSI

by Kim Siang Khaw, Cheng Chen, Massimo Giovannozzi, Tianqi Hu, Meng Lv, Jun Kai Ng, Angela Papa, Philipp Schmidt-Wellenburg, Bastiano Vitali and Guan Ming Wong

Phys. Sci. Forum 2023, 8(1), 50; https://doi.org/10.3390/psf2023008050 - 4 Sep 2023

Cited by 2 | Viewed by 1581

Abstract

Permanent electric dipole moments (EDMs) are excellent probes of physics beyond the Standard Model, especially on new sources of CP violation. The muon EDM has recently attracted significant attention due to discrepancies in the magnetic anomaly of the muon, as well as potential [...] Read more.

Permanent electric dipole moments (EDMs) are excellent probes of physics beyond the Standard Model, especially on new sources of CP violation. The muon EDM has recently attracted significant attention due to discrepancies in the magnetic anomaly of the muon, as well as potential violations of lepton-flavor universality in B-meson decays. At the Paul Scherrer Institute in Switzerland, we have proposed a muon EDM search experiment employing the frozen-spin technique, where a radial electric field is exerted within a storage solenoid to cancel the muon’s anomalous spin precession. Consequently, the EDM signal can be inferred from the upstream-downstream asymmetry of the decay positron count versus time. The experiment is planned to take place in two phases, anticipating an annual statistical sensitivity of

3 \times 10^{- 21}

e \cdot

cm for Phase I and

6 \times 10^{- 23}

e \cdot

cm for Phase II. Going beyond

10^{- 21}

e \cdot

cm will enable us to probe various Standard Model extensions. Full article

(This article belongs to the Proceedings of The 23rd International Workshop on Neutrinos from Accelerators)

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16 pages, 75254 KiB

Open AccessEditor’s ChoiceArticle

Electric Field-Induced Nano-Assembly Formation: First Evidence of Silicon Superclusters with a Giant Permanent Dipole Moment

by Fatme Jardali, Jacqueline Tran, Frédéric Liège, Ileana Florea, Mohamed E. Leulmi and Holger Vach

Nanomaterials 2023, 13(15), 2169; https://doi.org/10.3390/nano13152169 - 26 Jul 2023

Cited by 1 | Viewed by 1721

Abstract

The outstanding properties of silicon nanoparticles have been extensively investigated during the last few decades. Experimental evidence and applications of their theoretically predicted permanent electric dipole moment, however, have only been reported for silicon nanoclusters (SiNCs) for a size of about one to [...] Read more.

The outstanding properties of silicon nanoparticles have been extensively investigated during the last few decades. Experimental evidence and applications of their theoretically predicted permanent electric dipole moment, however, have only been reported for silicon nanoclusters (SiNCs) for a size of about one to two nanometers. Here, we have explored the question of whether suitable plasma conditions could lead to much larger silicon clusters with significantly stronger permanent electric dipole moments. A pulsed plasma approach was used for SiNC production and surface deposition. The absorption spectra of the deposited SiNCs were recorded using enhanced darkfield hyperspectral microscopy and compared to time-dependent DFT calculations. Atomic force microscopy and transmission electron microscopy observations completed our study, showing that one-to-two-nanometer SiNCs can, indeed, be used to assemble much larger ”superclusters” with a size of tens of nanometers. These superclusters possess extremely high permanent electric dipole moments that can be exploited to orient and guide these clusters with external electric fields, opening the path to the controlled architecture of silicon nanostructures. Full article

(This article belongs to the Special Issue Self-Assembly of Atomically Precise Nanoclusters: From Irregular Assembly to Crystalline Assembly)

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14 pages, 2234 KiB

Open AccessArticle

Impact of the Protein Environment on Two-Photon Absorption Cross-Sections of the GFP Chromophore Anion Resolved at the XMCQDPT2 Level of Theory

by Vladislav R. Aslopovsky, Andrei V. Scherbinin, Nadezhda N. Kleshchina and Anastasia V. Bochenkova

Int. J. Mol. Sci. 2023, 24(14), 11266; https://doi.org/10.3390/ijms241411266 - 10 Jul 2023

Cited by 3 | Viewed by 2595

Abstract

The search for fluorescent proteins with large two-photon absorption (TPA) cross-sections and improved brightness is required for their efficient use in bioimaging. Here, we explored the impact of a single-point mutation close to the anionic form of the GFP chromophore on its TPA [...] Read more.

The search for fluorescent proteins with large two-photon absorption (TPA) cross-sections and improved brightness is required for their efficient use in bioimaging. Here, we explored the impact of a single-point mutation close to the anionic form of the GFP chromophore on its TPA activity. We considered the lowest-energy transition of EGFP and its modification EGFP T203I. We focused on a methodology for obtaining reliable TPA cross-sections for mutated proteins, based on conformational sampling using molecular dynamics simulations and a high-level XMCQDPT2-based QM/MM approach. We also studied the numerical convergence of the sum-over-states formalism and provide direct evidence for the applicability of the two-level model for calculating TPA cross-sections in EGFP. The calculated values were found to be very sensitive to changes in the permanent dipole moments between the ground and excited states and highly tunable by internal electric field of the protein environment. In the case of the GFP chromophore anion, even a single hydrogen bond was shown to be capable of drastically increasing the TPA cross-section. Such high tunability of the nonlinear photophysical properties of the chromophore anions can be used for the rational design of brighter fluorescent proteins for bioimaging using two-photon laser scanning microscopy. Full article

(This article belongs to the Topic Theoretical, Quantum and Computational Chemistry)

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24 pages, 10272 KiB

Open AccessArticle

Physical Mechanism of Nonlinear Spectra in Triangene

by Na Zhang, Weijian Feng, Hanbo Wen, Naixing Feng, Hao Sheng, Zhixiang Huang and Jingang Wang

Molecules 2023, 28(9), 3744; https://doi.org/10.3390/molecules28093744 - 26 Apr 2023

Cited by 2 | Viewed by 1930

Abstract

In this work, we theoretically investigate the linear and nonlinear optical absorption properties of open triangulene spin chains and cyclic triangulene spin chains in relation to their lengths and shapes. The physical mechanism of local excitation within the triangular alkene unit and the [...] Read more.

In this work, we theoretically investigate the linear and nonlinear optical absorption properties of open triangulene spin chains and cyclic triangulene spin chains in relation to their lengths and shapes. The physical mechanism of local excitation within the triangular alkene unit and the weak charge transfer between the units are discussed. The uniformly distributed electrostatic potential allows the system to have a small permanent dipole moment that blocks the electronic transition in the light excitation such that the electronic transition can only be carried out between adjacent carbon atoms. The one-photon absorption (OPA) spectra and two-photon absorption (TPA) spectra are red-shifted with the addition of triangulene units compared to N = 3TSCs (triangulene spin chains, TSCs). Here, TPA is mainly caused by the first step of the transition. The length of the spin chain has a significant adjustment effect on the photon cross-section. TSCs of different lengths and shapes can control chirality by adjusting the distribution of the electric dipole moment and transition magnetic dipole moment. These analyses reveal the photophysical properties of triangulene and provide a theoretical basis for studying the photophysical properties of triangulene and its derivatives. Full article

(This article belongs to the Special Issue Carbon Nanomaterials: Design and Applications)

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14 pages, 3171 KiB

Open AccessArticle

Precision Storage Rings for Electric Dipole Moment Searches: A Tool En Route to Physics Beyond-the-Standard-Model

by Hans Ströher, Sebastian M. Schmidt, Paolo Lenisa and Jörg Pretz

Particles 2023, 6(1), 385-398; https://doi.org/10.3390/particles6010020 - 2 Mar 2023

Cited by 2 | Viewed by 2316

Abstract

Electric Dipole Moments (EDM) of particles (leptons, nucleons, and light nuclei) are currently deemed one of the best indicators for new physics, i.e., phenomena which lie outside the Standard Model (SM) of elementary particle physics—so-called physics “Beyond-the-Standard-Model” (BSM). Since EDMs of the SM [...] Read more.

Electric Dipole Moments (EDM) of particles (leptons, nucleons, and light nuclei) are currently deemed one of the best indicators for new physics, i.e., phenomena which lie outside the Standard Model (SM) of elementary particle physics—so-called physics “Beyond-the-Standard-Model” (BSM). Since EDMs of the SM are vanishingly small, a finite permanent EDM would indicate charge-parity (CP) symmetry violation in addition to the well-known sources of the SM, and could explain the baryon asymmetry of the Universe, while an oscillating EDM would hint at a possible Dark Matter (DM) field comprising axions or axion-like particles (ALPs). A new approach exploiting polarized charged particles (proton, deuteron, ³He) in precision storage rings offers the prospect to push current experimental EDM upper limits significantly further, including the possibility of an EDM discovery. In this paper, we describe the scientific background and the steps towards the realization of a precision storage ring, which will make such measurements possible. Full article

(This article belongs to the Special Issue Strong Interactions in the Standard Model: Massless Bosons to Compact Stars)

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26 pages, 7366 KiB

Open AccessReview

Crystal Engineering to Avoid Pairing Dipolar Moments: The Case of 5-Nitrouracil, a Highly Polarizable Molecule

by Manuela Ramos Silva and Pedro Pereira da Silva

Crystals 2023, 13(1), 145; https://doi.org/10.3390/cryst13010145 - 13 Jan 2023

Cited by 1 | Viewed by 2299

Abstract

5-nitrouracil is a polarizable molecule with a permanent electric dipole moment. Its molecular properties caught the attention of physicists working on nonlinear optics or optoelectronics, but the translation of the molecular assets to the crystalline solid has not been straightforward. This review compares [...] Read more.

5-nitrouracil is a polarizable molecule with a permanent electric dipole moment. Its molecular properties caught the attention of physicists working on nonlinear optics or optoelectronics, but the translation of the molecular assets to the crystalline solid has not been straightforward. This review compares all the known crystal structures incorporating the neutral or ionic 5-nitrouracil, or the two species concomitantly, discussing the effect of the packing in the optimization of the crystalline optical properties. Two new centrosymmetric 5-nitrouracilate salts are also reported for the first time, showing extensive hydrogen bonding between anions and cations. This review also gathers data from nonlinear optical measurements of non-centrosymmetric crystals and thermal stabilities of known polymorphs, showing that a neutral 5-nitrouracil molecule in acentric crystalline environment allows efficient blue-light generation. Full article

(This article belongs to the Section Crystal Engineering)

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4 pages, 217 KiB

Open AccessArticle

Identical Particles Exchange Symmetry and the Electric Dipole Moment in Molecules

by Guglielmo M. Tino

Symmetry 2022, 14(11), 2397; https://doi.org/10.3390/sym14112397 - 13 Nov 2022

Cited by 2 | Viewed by 1674

Abstract

Based on fundamental symmetries, molecules cannot have a permanent electric dipole moment, although it is commonly used in the literature to explain the different molecular spectra for heteronuclear and homonuclear molecules. Electric-dipole rotational and vibrational spectra can indeed be observed in heteronuclear molecules, [...] Read more.

Based on fundamental symmetries, molecules cannot have a permanent electric dipole moment, although it is commonly used in the literature to explain the different molecular spectra for heteronuclear and homonuclear molecules. Electric-dipole rotational and vibrational spectra can indeed be observed in heteronuclear molecules, while they are missing in molecules with identical nuclei. This paper shows that the missing spectral features can be explained as an effect of the exchange symmetry for identical particles. Full article

(This article belongs to the Special Issue Symmetry and Pauli Exclusion Principle)

17 pages, 2953 KiB

Open AccessArticle

Conformer Selection by Electrostatic Hexapoles: A Theoretical Study on 1-Chloroethanol and 2-Chloroethanol

by Concetta Caglioti, Masaaki Nakamura, Dock-Chil Che, Po-Yu Tsai and Federico Palazzetti

Symmetry 2022, 14(2), 317; https://doi.org/10.3390/sym14020317 - 4 Feb 2022

Cited by 2 | Viewed by 2342

Abstract

The electrostatic hexapole is a versatile device that has been used for many years in gas-phase experiments. Its inhomogeneous electric field has been employed for many purposes such as the selection of rotational states, the selection of clusters, the focusing of molecular beams, [...] Read more.

The electrostatic hexapole is a versatile device that has been used for many years in gas-phase experiments. Its inhomogeneous electric field has been employed for many purposes such as the selection of rotational states, the selection of clusters, the focusing of molecular beams, and molecular alignment as a precursor for molecular orientation. In the last few years, the hexapolar electric field has been demonstrated to be able to control the conformer composition of molecular beams. The key point is that conformers, where the component of the permanent electric dipole moment with respect to the largest of the principal axes of inertia is close to zero, require more intense hexapolar electric fields to be focused with respect to the other conformers. Here, we simulated the focusing curves of the conformers of 1-chloroethanol and 2-chloroethanol under hypothetical beam conditions, identical for all conformers, in a hypothetical and realistic experimental setup with three different hexapole lengths: 0.5, 1, and 2 m. The objective was to characterize this selection process to set up collision experiments on conformer-selected beams that provide information on the van der Waals clusters formed in collision processes. Full article

(This article belongs to the Special Issue Reactions, Structures, and Properties of Small Clusters: Experiments and Theory)

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5 pages, 326 KiB

Open AccessProceeding Paper

Nonlinear Optical Rectification in a Polar Molecule-Plasmonic Nanoparticle Structure

by Natalia Domenikou, Ioannis Thanopulos, Vassilios Yannopapas and Emmanuel Paspalakis

Mater. Proc. 2021, 4(1), 8; https://doi.org/10.3390/IOCN2020-07873 - 11 Nov 2020

Viewed by 1198

Abstract

We theoretically study the nonlinear optical rectification of a Zinc-phthalocyanine molecular complex, modelled as a polar two-level quantum system, interacting with an optical field near a gold nanoparticle. We use the steady-state solution of the density matrix equations for determining the nonlinear optical [...] Read more.

We theoretically study the nonlinear optical rectification of a Zinc-phthalocyanine molecular complex, modelled as a polar two-level quantum system, interacting with an optical field near a gold nanoparticle. We use the steady-state solution of the density matrix equations for determining the nonlinear optical rectification coefficient in this case. We further use first-principle electronic structure calculations for determining the energies of the molecular states involved and the corresponding transition and permanent electric dipole moments, as well as first-principle classical electromagnetic calculations for calculating the influence of the metallic nanoparticle on the decay rates of the molecular states due to the Purcell effect and on the external electric fields applied on the molecule. We investigate the nonlinear optical rectification coefficient in the absence and the presence of the plasmonic nanoparticle for various parameters, such as the field polarization and the distance between the molecular complex and the plasmonic nanoparticle. We find that the nonlinear coefficient can be significantly enhanced for specific field polarization and at suitable distance between the molecule and the plasmonic nanoparticle. We also find that this process is highly efficient at weak field intensity, zero pure dephasing rate and for small values of the transition dipole moment. Full article

(This article belongs to the Proceedings of The 2nd International Online-Conference on Nanomaterials)

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16 pages, 1661 KiB

Open AccessArticle

Significance of Non-Linear Terms in the Relativistic Coupled-Cluster Theory in the Determination of Molecular Properties

by V. Srinivasa Prasannaa, Bijaya K. Sahoo, Minori Abe and Bhanu P. Das

Symmetry 2020, 12(5), 811; https://doi.org/10.3390/sym12050811 - 13 May 2020

Cited by 5 | Viewed by 2945

Abstract

The relativistic coupled-cluster (RCC) theory has been applied recently to a number of heavy molecules to determine their properties very accurately. Since it demands large computational resources, the method is often approximated to single and double excitations (RCCSD method). The effective electric fields [...] Read more.

The relativistic coupled-cluster (RCC) theory has been applied recently to a number of heavy molecules to determine their properties very accurately. Since it demands large computational resources, the method is often approximated to single and double excitations (RCCSD method). The effective electric fields (

E_{e f f}

) and molecular permanent electric dipole moments (PDMs) of SrF, BaF, and mercury monohalides (HgX with X = F, Cl, Br, and I) molecules are of immense interest for probing fundamental physics. In our earlier calculations of

E_{e f f}

and PDMs for the above molecules, we neglected the non-linear terms in the property evaluation expression of the RCCSD method. In this work, we demonstrate the roles of these terms in determining the above quantities and their computational time scalability with the number of processors of a computer. We also compare our results with previous calculations that employed variants of RCC theory, as well as other many-body methods and available experimental values. Full article

(This article belongs to the Special Issue Development of New Methods in Atomic and Molecular Theory)

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11 pages, 1107 KiB

Open AccessCommunication

Searches for Electric Dipole Moments—Overview of Status and New Experimental Efforts

by Florian Kuchler and on behalf of the TUCAN and HeXeEDM Collaborations

Universe 2019, 5(2), 56; https://doi.org/10.3390/universe5020056 - 9 Feb 2019

Cited by 3 | Viewed by 3745

Abstract

Searches for permanent electric dipole moments (EDMs) of fundamental particles, atoms and molecules are promising experiments to constrain and potentially reveal beyond Standard Model (SM) physics. A non-zero EDM is a direct manifestation of time-reversal (T) violation, and, equivalently, violation of the combined [...] Read more.

Searches for permanent electric dipole moments (EDMs) of fundamental particles, atoms and molecules are promising experiments to constrain and potentially reveal beyond Standard Model (SM) physics. A non-zero EDM is a direct manifestation of time-reversal (T) violation, and, equivalently, violation of the combined operation of charge-conjugation (C) and parity inversion (P). Identifying new sources of CP violation can help to solve fundamental puzzles of the SM, e.g., the observed baryon-asymmetry in the Universe. Theoretical predictions for magnitudes of EDMs in the SM are many orders of magnitude below current experimental limits. However, many theories beyond the SM require larger EDMs. Experimental results, especially when combined in a global analysis, impose strong constraints on CP violating model parameters. Including an overview of EDM searches, I will focus on the future neutron EDM experiment at TRIUMF (Vancouver). For this effort, the TUCAN (TRIUMF Ultra Cold Advanced Neutron source) collaboration is aiming to build a strong, world leading source of ultra cold neutrons (UCN) based on a unique combination of a spallation target and a superfluid helium UCN converter. Another focus will be the search for an EDM of the diamagnetic atom

^{129}

Xe using a

^{3}

He comagnetometer and SQUID detection. The HeXeEDM collaboration has taken EDM data in 2017 and 2018 in the magnetically shielded room (BMSR-2) at PTB Berlin. Full article

(This article belongs to the Special Issue Selected Papers from the 7th International Conference on New Frontiers in Physics (ICNFP 2018))

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