Journal of Physics B: Atomic, Molecular and Optical Physics最新文献

{"title":"Tracking dissociation pathways of nitrobenzene via mega-electron-volt ultrafast electron diffraction","authors":"Kareem Hegazy, Phil Bucksbaum, Martin Centurion, James Cryan, Renkai Li, Ming-Fu Lin, Bryan Moore, Pedro Nunes, Xiaozhe Shen, Stephen Weathersby, Jie Yang, Xijie Wang, Thomas Wolf","doi":"10.1088/1361-6455/ad7431","DOIUrl":"https://doi.org/10.1088/1361-6455/ad7431","url":null,"abstract":"As the simplest nitroaromatic compound, nitrobenzene is an interesting model system to explore the rich photochemistry of nitroaromatic compounds. Previous investigations of nitrobenzene’s photochemical dynamics have probed structural and electronic properties. These investigations paint, at times, a convoluted and sometimes contradictory description of the photochemical landscape. We investigate the ultrafast dynamics of nitrobenzene triggered by photoexcitation at 267 nm for the first time using a structural probe with femtosecond time resolution. Our probe complements previous measurements of nitrobenzene’s electronic structure evolution and aids in determining the photochemical dynamics with less ambiguity. We employ megaelectronvolt ultrafast electron diffraction to follow nitrobenzene’s structural evolution within the first 5 ps after photoexcitation. We observe ground state recovery within <inline-formula>\u0000<tex-math><?CDATA $160 pm 60$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mn>160</mml:mn><mml:mo>±</mml:mo><mml:mn>60</mml:mn></mml:mrow></mml:math><inline-graphic xlink:href=\"bad7431ieqn1.gif\"></inline-graphic></inline-formula> fs through nonadiabatic dynamics. Based on comparisons of the experimental signal with molecular dynamics simulations, we exclude a significant population of the triplet manifold. Furthermore, we do not observe fragmentation of nitrobenzene within the investigated time window, which indicates that previously observed photofragmentation reactions take place in the vibrationally ‘hot’ ground state on timescales considerably beyond 5 ps.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"161 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Atom number fluctuations in Bose gases—statistical analysis of parameter estimation","authors":"T Vibel, M B Christensen, R M F Andersen, L N Stokholm, K Pawłowski, K Rzążewski, M A Kristensen, J J Arlt","doi":"10.1088/1361-6455/ad7458","DOIUrl":"https://doi.org/10.1088/1361-6455/ad7458","url":null,"abstract":"The investigation of atom number fluctuations in quantum gases at finite temperatures showcases the ongoing challenges in understanding complex quantum systems. Recently, the microcanonical nature of atom number fluctuations in weakly interacting Bose–Einstein condensates was observed. This motivates an investigation of the thermal component of partially condensed Bose gases, due to the conservation of the total atom number. Here, we present a combined analysis of both components, including a comprehensive analysis of the uncertainties in the preparation and parameter extraction of partially condensed quantum gases. This enables a complementary observation of the thermal atom number fluctuations and yields and improved value of the peak BEC atom number fluctuations <inline-formula>\u0000<tex-math><?CDATA $Delta N_mathrm{p,0}^2 = (3.7pm7)times10^5$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mi mathvariant=\"normal\">Δ</mml:mi><mml:msubsup><mml:mi>N</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">p</mml:mi><mml:mo>,</mml:mo><mml:mn>0</mml:mn></mml:mrow><mml:mn>2</mml:mn></mml:msubsup><mml:mo>=</mml:mo><mml:mo stretchy=\"false\">(</mml:mo><mml:mn>3.7</mml:mn><mml:mo>±</mml:mo><mml:mn>7</mml:mn><mml:mo stretchy=\"false\">)</mml:mo><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>5</mml:mn></mml:msup></mml:mrow></mml:math><inline-graphic xlink:href=\"bad7458ieqn1.gif\"></inline-graphic></inline-formula> close to the critical temperature. This corresponds to a reduction by 41% with respect to previous analysis and corroborates the microcanonical nature of the fluctuations. The analysis of noise contributions due to the preparation and evaluation of partially condensed Bose gases is based on Monte Carlo simulations of optical density profiles. Importantly, this allows for an estimation of the technical noise contributions to the atom number and temperature, which is generally applicable in the field of ultracold atoms.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"68 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anisotropy-driven magnetic phase transitions in SU(4)-symmetric Fermi gas in three-dimensional optical lattices","authors":"Vladyslav Unukovych, Andrii Sotnikov","doi":"10.1088/1361-6455/ad6b63","DOIUrl":"https://doi.org/10.1088/1361-6455/ad6b63","url":null,"abstract":"We study an SU(4)-symmetric ultracold fermionic mixture in a cubic optical lattice with a variable tunneling amplitude along one particular crystallographic axis in the crossover region from the two- to three-dimensional spatial geometry. To theoretically analyze the emerging magnetic phases and physical observables, we describe the system within the framework of the Fermi–Hubbard model and apply dynamical mean-field theory. We show that in two limiting cases of anisotropy, there are two phases with different antiferromagnetic orderings in the zero temperature limit and we determine a region of their coexistence. We also study the stability regions of different magnetically ordered states and density profiles of the gas in the harmonic optical trap.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"38 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Entanglement of a three-level atom interacting with two-modes field in a cavity","authors":"A del Rio-Lima, F J Poveda-Cuevas, O Castaños","doi":"10.1088/1361-6455/ad717d","DOIUrl":"https://doi.org/10.1088/1361-6455/ad717d","url":null,"abstract":"The dynamics of an atom of three levels in Λ configuration interacting with a quantized field of two modes in a cavity is studied within the rotating wave approximation by considering experimental values of accessible hyperfine levels of alkali atoms. The Hamiltonian model is constructed on the basis of the direct product of the atomic states with Fock states of light. This simplified basis allows us to generalize the state of light to any quantum field. The interaction term of the Hamiltonian restricts the system to a 3D Hilbert space. The system’s time evolution results show some similarities with the effective two-level system, such as the presence of collapses and revivals and the atom-field entanglement. By an analysis of the statistics of the photons, we show that when the three-level atom is interacting with a coherent field of two modes, it is possible to control experimentally the statistics of the field to be super-Poissonian or sub-Poissonian by the choice of the initial atomic state.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"121 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polarization spectroscopy of 87Rb-D2 line using structured light: controlling the line shape of closed hyperfine transition","authors":"Samim Akhtar, Aparajita Das, Md Mabud Hossain","doi":"10.1088/1361-6455/ad717c","DOIUrl":"https://doi.org/10.1088/1361-6455/ad717c","url":null,"abstract":"In this article, we present the influence of structured light on the line shape of closed hyperfine transition <inline-formula>\u0000<tex-math><?CDATA $F = 2 rightarrow F^{^{prime}} = 3$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mi>F</mml:mi><mml:mo>=</mml:mo><mml:mn>2</mml:mn><mml:mo stretchy=\"false\">→</mml:mo><mml:msup><mml:mi>F</mml:mi><mml:mrow><mml:mi>′</mml:mi></mml:mrow></mml:msup><mml:mo>=</mml:mo><mml:mn>3</mml:mn></mml:mrow></mml:math><inline-graphic xlink:href=\"bad717cieqn1.gif\"></inline-graphic></inline-formula> of ⁸⁷Rb-D₂ line by monitoring the linearly polarized probe Gaussian beam in the presence of circularly polarized pump Laguerre–Gaussian (LG) beam having different orders of orbital angular momentum (OAM). It is observed that both the amplitude and line-width of the closed hyperfine signal under polarization spectroscopy (PS) are enhanced (reduced) with the increasing values of the pump light ellipticity for the non-zero-order (zero-order) OAM. Furthermore, the dispersion-like PS signal of the closed hyperfine transition is modified by varying the pump power and angular mismatch of the pump-probe beams. The experimental results demonstrate that the anisotropy of an atomic medium can be influenced by the OAM of light and can be further modulated by tuning the ellipticity of the structured light.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"9 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protocols for x-ray transient grating pump/optical probe experiments at x-ray free electron lasers","authors":"Danny Fainozzi, Riccardo Cucini, Joan Vila-Comamala, Frederico Lima, Fernando Ardana-Lamas, Luis Bañares, Matias Bargheer, Filippo Bencivenga, Nadia Berndt, Martin Beye, Mykola Biednov, Stefano Bonetti, Marta Brioschi, Andrea Cannizzo, Pietro Carrara, Majed Chergui, Christian David, Robin Y Engel, Eugenio Ferrari, Thomas Feurer, Paul Frankenberger, Wojciech M Gawelda, Alessandro Gessini, Siti Heder, Xinchao Huang, Nupur N Khatu, Martin Knoll, Anders Madsen, Talgat Mamyrbayev, Claudio Masciovecchio, Alexei A Maznev, Christopher Milne, Riccardo Mincigrucci, Keith A Nelson, Ettore Paltanin, Giorgio Rossi, Markus Scholz, Carles Serrat, Urs Staub, Jakub Szlachetko, Renato Torre, Mano R Dhanalakshmi-Veeraraj, Han Xu, Peter Zalden, Cristian Svetina","doi":"10.1088/1361-6455/ad717f","DOIUrl":"https://doi.org/10.1088/1361-6455/ad717f","url":null,"abstract":"Transient grating spectroscopy is a specialized application of the four-wave-mixing methodology and constitutes a versatile technique for investigating the dynamics of vibrational, magnetic and electronic degrees of freedom of matter in a background-free fashion. Recent developments in free-electron laser sources have enabled the extension of this technique into the extreme ultraviolet range. Ongoing efforts to expand transient grating spectroscopy into the x-ray regime promise numerous advantages: (1) substantial penetration depths that allow for probing bulk material properties, (2) element specificity via specific core-excited states, and (3) short wavelengths that allow for excitation gratings with higher momentum transfer and improved spatial resolution. In this study, we comprehensively outline the procedures for conducting x-ray transient grating pump/optical probe experiment. The process encompasses the design and alignment of the experimental setup, as well as the subsequent steps involved in data acquisition and analysis. This paper is intended as a comprehensive guide for researchers interested in implementing x-ray transient grating spectroscopy, providing valuable insights into the intricacies of the experimental workflow required for this novel technique. Furthermore, we discuss the potential for extending this methodology to an x-ray pump/x-ray probe scheme, envisioning a future direction that holds promise for enhancing the capabilities and scope of x-ray transient grating spectroscopy, opening new opportunities for studying ultrafast processes with unprecedented temporal and spatial resolutions.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"13 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering and control of the entanglement for four Magnon modes inside two microwave cavities","authors":"Ziyad Imara, Khadija El Anouz, Abderrahim El Allati","doi":"10.1088/1361-6455/ad717e","DOIUrl":"https://doi.org/10.1088/1361-6455/ad717e","url":null,"abstract":"We present a model for investigating the entanglement features of four magnon modes in four yttrium-iron-garnet spheres dispersed in two microwave cavities (each cavity containing two spheres), which are driven by a squeezed field under actual experimental conditions. Each two-magnon mode inside each cavity is coupled via a beam splitter. We solve the covariance matrix associated with the four magnons, taking into account the relevant physical parameters. To quantify the degree of entanglement, we use the logarithmic negativity measure. Our study focuses on two parts. First, we study the entanglement properties between magnon modes by modifying the system parameters, and comparing the results with those obtained when we use a single magnon in each cavity, i.e. when one of the two magnons is not coupled to the cavity. In the second part, we give a new method for enhancing and controlling entanglement between magnon modes. We analyze the case where one of the two magnons is not coupled to the cavity, which can result a significant entanglement. Indeed, this goal is met in our situation by including an effective magnon–magnon coupling into both cavities. However, at high temperatures, the entanglement is almost completely broken. It can withstand temperatures of up to hundreds of millikelvin when using an experimentally accessible two-mode squeezed source.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"3 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic field enhanced laser absorption on a metallic surface incorporated with shape-dependent nanostructures","authors":"Moses Simon, Prashant Chauhan","doi":"10.1088/1361-6455/ad6b68","DOIUrl":"https://doi.org/10.1088/1361-6455/ad6b68","url":null,"abstract":"This communication proposes an analytical model to investigate the nanoparticle-based nonlinear absorption phenomenon associated with an obliquely incident p-polarized laser beam on a metallic surface. In this scheme, the surface is ingrained with noble-metal spherical nanoparticles and cylindrical nanoparticles in the presence of an external static magnetic field. The absorption of laser energy in the presence of nanoparticles (NPs) is attributed to surface plasmon resonance and enhanced magnetic-field effects. The absorption phenomenon is significantly enhanced by the incorporation of nanostructures and a magnetic field. The ellipticity characterizing parameter, which significantly influences the resonant frequency of different nanometric structures, has also been analysed and discussed. The effects of varying the magnetic field intensity, incident angle, size, and spacing of the NP were examined to determine their influence on the anomalous absorption of the laser. Furthermore, a direct dependency was found between the absorption coefficient and transmission coefficient of the incident laser, as well as the dimensions of the NPs. Several applications have direct relevance to this study, including biosensors such as DNA sensors and immunosensors, photothermal therapy, photoacoustic imaging, optoelectronic devices, solar cells, and surface-enhanced Raman spectroscopy.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"68 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ionization by radiative energy transport vs. impact ionization in energetic atomic collisions","authors":"A Jacob, C Müller, A B Voitkiv","doi":"10.1088/1361-6455/ad6b64","DOIUrl":"https://doi.org/10.1088/1361-6455/ad6b64","url":null,"abstract":"We explore a mechanism for ionization in high-velocity (but not yet relativistic) collisions of light atomic particles, one of which being initially in an excited internal state. This mechanism is driven by the generalized Breit interaction and proceeds via radiative energy transport between the colliding particles which has an extremely long range. A comparison of this mechanism with those which are ‘standard’ for high-velocity collisions shows that it can play a noticeable role in collisions with excited target atoms.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"79 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study on rotational energy transfer in LiH (X1 ∑+ v) + Ar collisions","authors":"Zilei Yu, Xiaofang Zhao, Shuying Wang, Chu Qin, Yifan Shen, Kang Dai","doi":"10.1088/1361-6455/ad6b67","DOIUrl":"https://doi.org/10.1088/1361-6455/ad6b67","url":null,"abstract":"Using high-resolution transient laser spectroscopy, the rotational energy transfer between LiH (12, 8) and Ar through collisions was studied. LiH (12, 8) was generated via degenerate stimulated hyper-Raman scattering. The population of LiH (12, <italic toggle=\"yes\">J″</italic> ≠ 8) generated during collisions were obtained using transient laser-induced fluorescence. According to the rate equation, the rate coefficients for the transfer from (12, 8) to (12, <italic toggle=\"yes\">J″</italic>) states are between 7.1 × 10⁻¹² and 3.5 × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ within 2 <italic toggle=\"yes\">μ</italic>s of the collision occurring. Above 2 <italic toggle=\"yes\">μ</italic>s, the rate coefficient is no longer constant. Meanwhile, no vibrational relaxation occurs before 10 <italic toggle=\"yes\">μ</italic>s. The rotational energy <italic toggle=\"yes\">E</italic>_rot is the sum of the rotational energies of rotational states (12, <italic toggle=\"yes\">J″</italic>). Within the period of 0–10 <italic toggle=\"yes\">μ</italic>s, the value of <italic toggle=\"yes\">E</italic>_rot decreases from 541 cm⁻¹ to 390 cm⁻¹. The distribution of translational energy <italic toggle=\"yes\">E</italic>_trans at different delay time of LiH (12, 8) is obtained by measuring the Doppler broadened line widths. It increases from 707 cm⁻¹ at 0 <italic toggle=\"yes\">μ</italic>s to 852 cm⁻¹ at 10 <italic toggle=\"yes\">μ</italic>s. Therefore, when rotational relaxation occurs, the decrease in rotational energy is approximately equal to the increase in translational energy.","PeriodicalId":16826,"journal":{"name":"Journal of Physics B: Atomic, Molecular and Optical Physics","volume":"68 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142190793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}