J. P. Cassidy, J. Hofierka, B. Cunningham, D. G. Green
The energetic stability of positron di-anion systems [A$^-;e^+;$A$^-$] is studied via many-body theory, where $A^-$ includes H$^{-}$, F$^{-}$, Cl$^{-}$ and the molecular anions (CN)$^{-}$ and (NCO)$^{-}$. Specifically, the energy of the system as a function of ionic separation is determined by solving the Dyson equation for the positron in the field of the two anions, using a positron-anion self energy as constructed in [J. Hofierka, B. Cunningham, C. M. Rawlins, C. H. Patterson and D. G. Green, emph{Nature} {bf 606} 688 (2022)] that accounts for correlations including polarization, screening, and virtual-positronium formation. Calculations are performed for a positron interacting with H$_{2}^{2-}$, F$_{2}^{2-}$, and Cl$_{2}^{2-}$, and are found to be in good agreement with previous theory. In particular, we confirm the presence of two minima in the potential energy of the [H$^-;e^+$;H$^-$] system with respect to ionic separation: one a positronically-bonded [H$^-;e^+$;H$^-$] local minimum at ionic separations $rsim3.4$~AAphantom{}, and a global minimum at smaller ionic separations $rlesssim1.6$~AAphantom{} that gives overall instability of the system with respect to dissociation into a H$_2$ molecule and a positronium negative ion, Ps$^-$. The first predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)$_{2}^{2-}$, and (NCO)$_{2}^{2-}$. In all cases we find that the molecules formed by the creation of a positronic bond are stable relative to dissociation into A$^-$ and $e^+$A$^-$ (positron bound to a single anion), with bond energies on the order of 1~eV and bond lengths on the order of several r angstroms.
{"title":"Many-body theory calculations of positronic-bonded molecular dianions","authors":"J. P. Cassidy, J. Hofierka, B. Cunningham, D. G. Green","doi":"arxiv-2311.16318","DOIUrl":"https://doi.org/arxiv-2311.16318","url":null,"abstract":"The energetic stability of positron di-anion systems [A$^-;e^+;$A$^-$] is\u0000studied via many-body theory, where $A^-$ includes H$^{-}$, F$^{-}$, Cl$^{-}$\u0000and the molecular anions (CN)$^{-}$ and (NCO)$^{-}$. Specifically, the energy\u0000of the system as a function of ionic separation is determined by solving the\u0000Dyson equation for the positron in the field of the two anions, using a\u0000positron-anion self energy as constructed in [J. Hofierka, B. Cunningham, C. M.\u0000Rawlins, C. H. Patterson and D. G. Green, emph{Nature} {bf 606} 688 (2022)]\u0000that accounts for correlations including polarization, screening, and\u0000virtual-positronium formation. Calculations are performed for a positron\u0000interacting with H$_{2}^{2-}$, F$_{2}^{2-}$, and Cl$_{2}^{2-}$, and are found\u0000to be in good agreement with previous theory. In particular, we confirm the\u0000presence of two minima in the potential energy of the [H$^-;e^+$;H$^-$] system\u0000with respect to ionic separation: one a positronically-bonded [H$^-;e^+$;H$^-$]\u0000local minimum at ionic separations $rsim3.4$~AAphantom{}, and a global\u0000minimum at smaller ionic separations $rlesssim1.6$~AAphantom{} that gives\u0000overall instability of the system with respect to dissociation into a H$_2$\u0000molecule and a positronium negative ion, Ps$^-$. The first predictions are made\u0000for positronic bonding in dianions consisting of molecular anionic fragments,\u0000specifically for (CN)$_{2}^{2-}$, and (NCO)$_{2}^{2-}$. In all cases we find\u0000that the molecules formed by the creation of a positronic bond are stable\u0000relative to dissociation into A$^-$ and $e^+$A$^-$ (positron bound to a single\u0000anion), with bond energies on the order of 1~eV and bond lengths on the order\u0000of several r angstroms.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anna Dawid, Niccolò Bigagli, Daniel W. Savin, Sebastian Will
One of the demanding frontiers in ultracold science is identifying laser cooling schemes for complex atoms and molecules, out of their vast spectra of internal states. Motivated by a need to expand the set of available ultracold molecules for applications in fundamental physics, chemistry, astrochemistry, and quantum simulation, we propose and demonstrate an automated graph-based search approach for viable laser cooling schemes. The method is time efficient and the outcomes greatly surpass the results of manual searches used so far. We discover new laser cooling schemes for C$_2$, OH$^+$, CN, YO, and CO$_2$ that can be viewed as surprising or counterintuitive compared to previously identified laser cooling schemes. In addition, a central insight of this work is that the reinterpretation of quantum states and transitions between them as a graph can dramatically enhance our ability to identify new quantum control schemes for complex quantum systems. As such, this approach will also be applicable to complex atoms and, in fact, any complex many-body quantum system with a discrete spectrum of internal states.
{"title":"Automated detection of laser cooling schemes for ultracold molecules","authors":"Anna Dawid, Niccolò Bigagli, Daniel W. Savin, Sebastian Will","doi":"arxiv-2311.08381","DOIUrl":"https://doi.org/arxiv-2311.08381","url":null,"abstract":"One of the demanding frontiers in ultracold science is identifying laser\u0000cooling schemes for complex atoms and molecules, out of their vast spectra of\u0000internal states. Motivated by a need to expand the set of available ultracold\u0000molecules for applications in fundamental physics, chemistry, astrochemistry,\u0000and quantum simulation, we propose and demonstrate an automated graph-based\u0000search approach for viable laser cooling schemes. The method is time efficient\u0000and the outcomes greatly surpass the results of manual searches used so far. We\u0000discover new laser cooling schemes for C$_2$, OH$^+$, CN, YO, and CO$_2$ that\u0000can be viewed as surprising or counterintuitive compared to previously\u0000identified laser cooling schemes. In addition, a central insight of this work\u0000is that the reinterpretation of quantum states and transitions between them as\u0000a graph can dramatically enhance our ability to identify new quantum control\u0000schemes for complex quantum systems. As such, this approach will also be\u0000applicable to complex atoms and, in fact, any complex many-body quantum system\u0000with a discrete spectrum of internal states.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Enliang Wang, Surjendu Bhattacharyya, Keyu Chen, Kurtis Borne, Farzaneh Ziaee, Shashank Pathak, Huynh Van Sa Lam, Anbu Selvam Venkatachalam, Xiangjun Chen, Rebecca Boll, Till Jahnke, Artem Rudenko, Daniel Rolles
Following the changes in molecular structure throughout the entirety of a chemical reaction with atomic resolution is a long-term goal in femtochemistry. Although the development of a plethora of ultrafast technique has enabled detailed investigations of the electronic and nuclear dynamics on femtosecond time scales, direct and unambiguous imaging of the nuclear motion during a reaction is still a major challenge. Here, we apply time-resolved Coulomb explosion imaging with femtosecond near-infrared pulses to visualize the ultraviolet-induced ultrafast molecular dynamics of gas-phase furan. Widely contradicting predictions and observations for this molecule have been reported in the literature. By combining the experimental Coulomb explosion imaging data with ab initio molecular dynamics and Coulomb explosion simulations, we reveal the presence of a strong ultrafast ring-opening pathway upon excitation at 198 nm that occurs within 100 fs.
{"title":"Time-Resolved Coulomb Explosion Imaging Unveils Ultrafast Ring Opening of Furan","authors":"Enliang Wang, Surjendu Bhattacharyya, Keyu Chen, Kurtis Borne, Farzaneh Ziaee, Shashank Pathak, Huynh Van Sa Lam, Anbu Selvam Venkatachalam, Xiangjun Chen, Rebecca Boll, Till Jahnke, Artem Rudenko, Daniel Rolles","doi":"arxiv-2311.05099","DOIUrl":"https://doi.org/arxiv-2311.05099","url":null,"abstract":"Following the changes in molecular structure throughout the entirety of a\u0000chemical reaction with atomic resolution is a long-term goal in femtochemistry.\u0000Although the development of a plethora of ultrafast technique has enabled\u0000detailed investigations of the electronic and nuclear dynamics on femtosecond\u0000time scales, direct and unambiguous imaging of the nuclear motion during a\u0000reaction is still a major challenge. Here, we apply time-resolved Coulomb\u0000explosion imaging with femtosecond near-infrared pulses to visualize the\u0000ultraviolet-induced ultrafast molecular dynamics of gas-phase furan. Widely\u0000contradicting predictions and observations for this molecule have been reported\u0000in the literature. By combining the experimental Coulomb explosion imaging data\u0000with ab initio molecular dynamics and Coulomb explosion simulations, we reveal\u0000the presence of a strong ultrafast ring-opening pathway upon excitation at 198\u0000nm that occurs within 100 fs.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. V. Begunovich, E. A. Kovaleva, M. M. Korshunov, V. F. Shabanov
We've studied the B800 part of Rhodoblastus acidophilus light-harvesting complex (LH2) by several quantum chemical techniques based on the density functional theory (DFT) and determined the specific method and a minimal reliable model suitable for further studies of the LH2. In addition to bacteriochlorophyll a molecules, the minimal model includes two $alpha$ and one $beta$ chain amino acids. Within the model, we are able to reproduce the contribution of the B800 ring of nine bacteriochlorophyll a molecules to the near infrared $Q_y$ absorption band. We also discuss the use of hybrid DFT calculations for precise energy and optical estimations and DFT-based tight binding (DFTB) method for the large-scale calculations. Crucial importance of Hartree-Fock exchange interaction for the correct description of B800 peak position was shown.
{"title":"Absorption spectra of the purple nonsulfur bacteria light-harvesting complex: a DFT study of the B800 part","authors":"L. V. Begunovich, E. A. Kovaleva, M. M. Korshunov, V. F. Shabanov","doi":"arxiv-2311.02024","DOIUrl":"https://doi.org/arxiv-2311.02024","url":null,"abstract":"We've studied the B800 part of Rhodoblastus acidophilus light-harvesting\u0000complex (LH2) by several quantum chemical techniques based on the density\u0000functional theory (DFT) and determined the specific method and a minimal\u0000reliable model suitable for further studies of the LH2. In addition to\u0000bacteriochlorophyll a molecules, the minimal model includes two $alpha$ and\u0000one $beta$ chain amino acids. Within the model, we are able to reproduce the\u0000contribution of the B800 ring of nine bacteriochlorophyll a molecules to the\u0000near infrared $Q_y$ absorption band. We also discuss the use of hybrid DFT\u0000calculations for precise energy and optical estimations and DFT-based tight\u0000binding (DFTB) method for the large-scale calculations. Crucial importance of\u0000Hartree-Fock exchange interaction for the correct description of B800 peak\u0000position was shown.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"239 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigate the dynamics of a spin system with facilitation constraint that can be studied using Rydberg atoms in arrays of optical tweezer traps. The elementary degrees of freedom of the system are domains of Rydberg excitations that expand ballistically through the lattice. Due to mechanical forces, Rydberg excited atoms are coupled to vibrations within their traps. At zero temperature and large trap depth, it is known that virtually excited lattice vibrations only renormalize the timescale of the ballistic propagation. However, when vibrational excitations are initially present -- i.e., when the external motion of the atoms is prepared in an excited Fock state, coherent state or thermal state -- resonant scattering between spin domain walls and phonons takes place. This coherent and deterministic process, which is free from disorder, leads to a reduction of the power-law exponent characterizing the expansion of spin domains. Furthermore, the spin domain dynamics is sensitive to the coherence properties of the atoms' vibrational state, such as the relative phase of coherently superimposed Fock states. Even for a translationally invariant initial state the latter manifests macroscopically in a phase-sensitive asymmetric expansion.
{"title":"Coherent spin-phonon scattering in facilitated Rydberg lattices","authors":"Matteo Magoni, Chris Nill, Igor Lesanovsky","doi":"arxiv-2311.00064","DOIUrl":"https://doi.org/arxiv-2311.00064","url":null,"abstract":"We investigate the dynamics of a spin system with facilitation constraint\u0000that can be studied using Rydberg atoms in arrays of optical tweezer traps. The\u0000elementary degrees of freedom of the system are domains of Rydberg excitations\u0000that expand ballistically through the lattice. Due to mechanical forces,\u0000Rydberg excited atoms are coupled to vibrations within their traps. At zero\u0000temperature and large trap depth, it is known that virtually excited lattice\u0000vibrations only renormalize the timescale of the ballistic propagation.\u0000However, when vibrational excitations are initially present -- i.e., when the\u0000external motion of the atoms is prepared in an excited Fock state, coherent\u0000state or thermal state -- resonant scattering between spin domain walls and\u0000phonons takes place. This coherent and deterministic process, which is free\u0000from disorder, leads to a reduction of the power-law exponent characterizing\u0000the expansion of spin domains. Furthermore, the spin domain dynamics is\u0000sensitive to the coherence properties of the atoms' vibrational state, such as\u0000the relative phase of coherently superimposed Fock states. Even for a\u0000translationally invariant initial state the latter manifests macroscopically in\u0000a phase-sensitive asymmetric expansion.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The impact of targeted replacement of individual terms in empirical force fields is quantitatively assessed for pure water, dichloromethane (DCM), and solvated K$^+$ and Cl$^-$ ions. For the electrostatics, point charges (PCs) and machine learning (ML)based minimally distributed charges (MDCM) fitted to the molecular electrostatic potential are evaluated together with electrostatics based on the Coulomb integral. The impact of explicitly including second-order terms is investigated by adding a fragment molecular orbital (FMO)-derived polarization energy to an existing force field, in this case CHARMM. It is demonstrated that anisotropic electrostatics reduce the RMSE for water (by 1.6 kcal/mol), DCM (by 0.8 kcal/mol) and for solvated Cl$^-$ clusters (by 0.4 kcal/mol). An additional polarization term can be neglected for DCM but notably improves errors in pure water (by 1.1 kcal/mol) and in Cl$^-$ clusters (by 0.4 kcal/mol) and is key to describing solvated K$^+$, reducing the RMSE by 2.3 kcal/mol. A 12-6 Lennard-Jones functional form is found to perform satisfactorily with PC and MDCM electrostatics, but is not appropriate for descriptions that account for the electrostatic penetration energy. The importance of many-body contributions is assessed by comparing a strictly 2-body approach with self-consistent reference data. DCM can be approximated well with a 2-body potential while water and solvated K$^+$ and Cl$^-$ ions require explicit many-body corrections. The present work systematically quantifies which terms improve the performance of an existing force field and what reference data to use for parametrizing these terms in a tractable fashion for ML fitting of pure and heterogeneous systems.
{"title":"Systematic Improvement of Empirical Energy Functions in the Era of Machine Learning","authors":"Mike Devereux, Eric D. Boittier, Makrus Meuwly","doi":"arxiv-2310.18655","DOIUrl":"https://doi.org/arxiv-2310.18655","url":null,"abstract":"The impact of targeted replacement of individual terms in empirical force\u0000fields is quantitatively assessed for pure water, dichloromethane (DCM), and\u0000solvated K$^+$ and Cl$^-$ ions. For the electrostatics, point charges (PCs) and\u0000machine learning (ML)based minimally distributed charges (MDCM) fitted to the\u0000molecular electrostatic potential are evaluated together with electrostatics\u0000based on the Coulomb integral. The impact of explicitly including second-order\u0000terms is investigated by adding a fragment molecular orbital (FMO)-derived\u0000polarization energy to an existing force field, in this case CHARMM. It is\u0000demonstrated that anisotropic electrostatics reduce the RMSE for water (by 1.6\u0000kcal/mol), DCM (by 0.8 kcal/mol) and for solvated Cl$^-$ clusters (by 0.4\u0000kcal/mol). An additional polarization term can be neglected for DCM but notably\u0000improves errors in pure water (by 1.1 kcal/mol) and in Cl$^-$ clusters (by 0.4\u0000kcal/mol) and is key to describing solvated K$^+$, reducing the RMSE by 2.3\u0000kcal/mol. A 12-6 Lennard-Jones functional form is found to perform\u0000satisfactorily with PC and MDCM electrostatics, but is not appropriate for\u0000descriptions that account for the electrostatic penetration energy. The\u0000importance of many-body contributions is assessed by comparing a strictly\u00002-body approach with self-consistent reference data. DCM can be approximated\u0000well with a 2-body potential while water and solvated K$^+$ and Cl$^-$ ions\u0000require explicit many-body corrections. The present work systematically\u0000quantifies which terms improve the performance of an existing force field and\u0000what reference data to use for parametrizing these terms in a tractable fashion\u0000for ML fitting of pure and heterogeneous systems.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lorenzo Contessi, Martin Schäfer, Ubirajara van Kolck
We present an improved action for renormalizable effective field theories (EFTs) of systems near the two-body unitarity limit. The ordering of EFT interactions is constrained, but not entirely fixed, by the renormalization group. The remaining freedom can be used to improve the theory's convergence, to simplify its applications, and to connect it to phenomenological models. We exemplify the method on a contact theory applied to systems of up to five $^4$He atoms. We solve the EFT at LO including a subleading interaction that accounts for part of the two-body effective range. We show that the effects of such fake range can be compensated in perturbation theory at NLO, as long as the fake range is smaller or comparable to the experimental effective range. These results open the possibility of using similar improved actions for other many-body systems.
{"title":"Improved action for contact effective field theory","authors":"Lorenzo Contessi, Martin Schäfer, Ubirajara van Kolck","doi":"arxiv-2310.15760","DOIUrl":"https://doi.org/arxiv-2310.15760","url":null,"abstract":"We present an improved action for renormalizable effective field theories\u0000(EFTs) of systems near the two-body unitarity limit. The ordering of EFT\u0000interactions is constrained, but not entirely fixed, by the renormalization\u0000group. The remaining freedom can be used to improve the theory's convergence,\u0000to simplify its applications, and to connect it to phenomenological models. We\u0000exemplify the method on a contact theory applied to systems of up to five\u0000$^4$He atoms. We solve the EFT at LO including a subleading interaction that\u0000accounts for part of the two-body effective range. We show that the effects of\u0000such fake range can be compensated in perturbation theory at NLO, as long as\u0000the fake range is smaller or comparable to the experimental effective range.\u0000These results open the possibility of using similar improved actions for other\u0000many-body systems.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"104 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Bastian, J. D. Asmussen, L. Ben Ltaief, H. B. Pedersen, K. Sishodia, S. De, S. R. Krishnan, C. Medina, N. Pal, R. Richter, N. Sisourat, M. Mudrich
Interatomic Coulombic decay (ICD) plays a crucial role in weakly bound complexes exposed to intense or high-energy radiation. So far, neutral or ionic atoms or molecules have been prepared in singly excited electron or hole states which can transfer energy to neighboring centers and cause ionization and radiation damage. Here we demonstrate that a doubly excited atom, despite its extremely short lifetime, can decay by ICD; evidenced by high-resolution photoelectron spectra of He nanodroplets excited to the 2s2p+ state. We find that ICD proceeds by relaxation into excited He$^*$He$^+$ atom-pair states, in agreement with calculations. The ability of inducing ICD by resonant excitation far above the single-ionization threshold opens opportunities for controlling radiation damage to a high degree of element specificity and spectral selectivity.
{"title":"Observation of interatomic Coulombic decay induced by double excitation of helium in nanodroplets","authors":"B. Bastian, J. D. Asmussen, L. Ben Ltaief, H. B. Pedersen, K. Sishodia, S. De, S. R. Krishnan, C. Medina, N. Pal, R. Richter, N. Sisourat, M. Mudrich","doi":"arxiv-2310.15835","DOIUrl":"https://doi.org/arxiv-2310.15835","url":null,"abstract":"Interatomic Coulombic decay (ICD) plays a crucial role in weakly bound\u0000complexes exposed to intense or high-energy radiation. So far, neutral or ionic\u0000atoms or molecules have been prepared in singly excited electron or hole states\u0000which can transfer energy to neighboring centers and cause ionization and\u0000radiation damage. Here we demonstrate that a doubly excited atom, despite its\u0000extremely short lifetime, can decay by ICD; evidenced by high-resolution\u0000photoelectron spectra of He nanodroplets excited to the 2s2p+ state. We find\u0000that ICD proceeds by relaxation into excited He$^*$He$^+$ atom-pair states, in\u0000agreement with calculations. The ability of inducing ICD by resonant excitation\u0000far above the single-ionization threshold opens opportunities for controlling\u0000radiation damage to a high degree of element specificity and spectral\u0000selectivity.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benchmarking a high-precision quantum operation is a big challenge for many quantum systems in the presence of various noises as well as control errors. Here we propose an $O(1)$ benchmarking of a dynamically corrected rotation by taking the quantum advantage of a squeezed spin state in a spin-1 Bose-Einstein condensate. Our analytical and numerical results show that tiny rotation infidelity, defined by $1-F$ with $F$ the rotation fidelity, can be calibrated in the order of $1/N^2$ by only several measurements of the rotation error for $N$ atoms in an optimally squeezed spin state. Such an $O(1)$ benchmarking is possible not only in a spin-1 BEC but also in other many-spin or many-qubit systems if a squeezed or entangled state is available.
{"title":"O(1) benchmarking of precise rotation in a spin-squeezed Bose-Einstein condensate","authors":"Peng Du, Hui Tang, Jun Zhang, Wenxian Zhang","doi":"arxiv-2310.15473","DOIUrl":"https://doi.org/arxiv-2310.15473","url":null,"abstract":"Benchmarking a high-precision quantum operation is a big challenge for many\u0000quantum systems in the presence of various noises as well as control errors.\u0000Here we propose an $O(1)$ benchmarking of a dynamically corrected rotation by\u0000taking the quantum advantage of a squeezed spin state in a spin-1 Bose-Einstein\u0000condensate. Our analytical and numerical results show that tiny rotation\u0000infidelity, defined by $1-F$ with $F$ the rotation fidelity, can be calibrated\u0000in the order of $1/N^2$ by only several measurements of the rotation error for\u0000$N$ atoms in an optimally squeezed spin state. Such an $O(1)$ benchmarking is\u0000possible not only in a spin-1 BEC but also in other many-spin or many-qubit\u0000systems if a squeezed or entangled state is available.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaoju Chang, Bo Chen, Qiyu Zeng, Han Wang, Kaiguo Chen, Qunchao Tong, Xiaoxiang Yu, Dongdong Kang, Shen Zhang, Fangyu Guo, Yong Hou, Zengxiu Zhao, Yansun Yao, Yanming Ma, Jiayu Dai
The immiscibility of hydrogen-helium mixture under the temperature and pressure conditions of planetary interiors is crucial for understanding the structures of gas giant planets (e.g., Jupiter and Saturn). While the experimental probe at such extreme conditions is challenging, theoretical simulation is heavily relied in an effort to unravel the mixing behavior of hydrogen and helium. Here we develop a method via a machine learning accelerated molecular dynamics simulation to quantify the physical separation of hydrogen and helium under the conditions of planetary interiors. The immiscibility line achieved with the developed method yields substantially higher demixing temperatures at pressure above 1.5 Mbar than earlier theoretical data, but matches better to the experimental estimate. Our results revise the structures of Jupiter and Saturn where H-He demixing takes place in a large fraction of the interior radii, i.e., 27.5% in Jupiter and 48.3% in Saturn. This direct evidence of an H-He immiscible layer supports the formation of helium rain and explains the helium reduction in atmosphere of Jupiter and Saturn.
{"title":"Direct evidence of helium rain in Jupiter and Saturn","authors":"Xiaoju Chang, Bo Chen, Qiyu Zeng, Han Wang, Kaiguo Chen, Qunchao Tong, Xiaoxiang Yu, Dongdong Kang, Shen Zhang, Fangyu Guo, Yong Hou, Zengxiu Zhao, Yansun Yao, Yanming Ma, Jiayu Dai","doi":"arxiv-2310.13412","DOIUrl":"https://doi.org/arxiv-2310.13412","url":null,"abstract":"The immiscibility of hydrogen-helium mixture under the temperature and\u0000pressure conditions of planetary interiors is crucial for understanding the\u0000structures of gas giant planets (e.g., Jupiter and Saturn). While the\u0000experimental probe at such extreme conditions is challenging, theoretical\u0000simulation is heavily relied in an effort to unravel the mixing behavior of\u0000hydrogen and helium. Here we develop a method via a machine learning\u0000accelerated molecular dynamics simulation to quantify the physical separation\u0000of hydrogen and helium under the conditions of planetary interiors. The\u0000immiscibility line achieved with the developed method yields substantially\u0000higher demixing temperatures at pressure above 1.5 Mbar than earlier\u0000theoretical data, but matches better to the experimental estimate. Our results\u0000revise the structures of Jupiter and Saturn where H-He demixing takes place in\u0000a large fraction of the interior radii, i.e., 27.5% in Jupiter and 48.3% in\u0000Saturn. This direct evidence of an H-He immiscible layer supports the formation\u0000of helium rain and explains the helium reduction in atmosphere of Jupiter and\u0000Saturn.","PeriodicalId":501259,"journal":{"name":"arXiv - PHYS - Atomic and Molecular Clusters","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138522613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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