- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
A tunable external cavity laser operating at excited states of bimodal-sized quantum-dot
摘要： In this paper, a tunable external cavity diode laser (ECDL) based on the first excited states of two independent quantum dot (QD) ensemble has been demonstrated. The device exhibits stabilized lasing with high power of 120 mW. We attribute the excellent output characteristics of the QD ECDL to carrier radiation recombination in high energy states, which has higher degeneracy than low energy states and can accommodate more carriers. The linewidth of ECDL is less than 0.2 nm, which is also much narrower than most of QD ECDLs as reported. Preliminary discussion attributes the spectra feature to the lower QD density and independent carrier transitions. The tunable range is 28.9 nm (970.1 ~ 999 nm) and the wavelength shift with the injection current is 0.7 nm/A.
关键词： tunable external cavity laser,bimodal-sized,quantum-dot,excited states
更新于2025-11-28 14:23:57
-
Application of polar solvent effects in absorption spectra for determination of lowest electron-excited states of phthalide
摘要： The optical absorption spectra of phthalide in polar (methanol) and nonpolar (n-hexane) solvents are recorded. The electronic phthalide spectrum was calculated by TDDFT B3LYP/6-311+G(d, p) using the polarisable continuum model. Based on an analysis of calculation data and the displacement of absorption bands in a polar solvent, it was established that the absorption bands of phthalide at energies of 3.51 and 3.96 eV correspond to singlet-triplet transitions to the T1 and T2 states, respectively.
关键词： Triplet excited states,Electronic absorption spectra,PCM TDDFT,Solvent effect,Phthalide
更新于2025-09-23 15:23:52
-
Quench dynamics of finite bosonic ensembles in optical lattices with spatially modulated interactions
摘要： The nonequilibrium quantum dynamics of few boson ensembles which experience a spatially modulated interaction strength and are confined in finite optical lattices is investigated. We utilize a cosinusoidal spatially modulated effective interaction strength which is characterized by its wavevector, inhomogeneity amplitude, interaction offset and a phase. Performing quenches either on the wavevector or the phase of the interaction profile an enhanced imbalance of the interatomic repulsion between distinct spatial regions of the lattice is induced. Following both quench protocols triggers various tunneling channels and a rich excitation dynamics consisting of a breathing and a cradle mode. All modes are shown to be amplified for increasing inhomogeneity amplitude of the interaction strength. Especially the phase quench induces a directional transport enabling us to discern energetically, otherwise, degenerate tunneling pathways. Moreover, a periodic population transfer between distinct momenta for quenches of increasing wavevector is observed, while a directed occupation of higher momenta can be achieved following a phase quench. Finally, during the evolution regions of partial coherence are revealed between the predominantly occupied wells.
关键词： nonequilibrium dynamics,spatially dependent interactions,excited states,few-body systems,quench dynamics,optical lattices
更新于2025-09-23 15:21:01
-
Prominent radiative contributions from multiply-excited states in laser-produced tin plasma for nanolithography
摘要： Extreme ultraviolet (EUV) lithography is currently entering high-volume manufacturing to enable the continued miniaturization of semiconductor devices. The required EUV light, at 13.5 nm wavelength, is produced in a hot and dense laser-driven tin plasma. The atomic origins of this light are demonstrably poorly understood. Here we calculate detailed tin opacity spectra using the Los Alamos atomic physics suite ATOMIC and validate these calculations with experimental comparisons. Our key finding is that EUV light largely originates from transitions between multiply-excited states, and not from the singly-excited states decaying to the ground state as is the current paradigm. Moreover, we find that transitions between these multiply-excited states also contribute in the same narrow window around 13.5 nm as those originating from singly-excited states, and this striking property holds over a wide range of charge states. We thus reveal the doubly magic behavior of tin and the origins of the EUV light.
关键词： multiply-excited states,tin plasma,EUV lithography,atomic physics,opacity spectra
更新于2025-09-23 15:21:01
-
A general approach for the calculation and characterization of x-ray absorption spectra
摘要： We present a general approach for the calculation and assignment of X-ray absorption spectra based on electronic wavepacket propagations performed using explicitly time-dependent electronic structure calculations. Such calculations have the appeal of yielding the entire absorption spectrum for the cost of a single set of electronic wavepacket propagations, obviating the need to explicitly calculate large numbers of core-excited states. The spectrum can either be calculated from the Fourier transform of the time-dependent dipole moment or from the Fourier transform of the wavepacket autocorrelation function. We propose that calculating the absorption spectrum using the latter approach will generally be the preferred option. This method has two important advantages. First, the autocorrelation functions can be obtained for twice the propagation time, resulting in a halving of the computational effort required to calculate the spectrum relative to the time-dependent dipole moment approach. Second, using the tools of filter diagonalisation, the autocorrelation functions may be used to determine the time-independent final core-excited states underlying the peaks of interest in the spectrum. The proposed scheme is validated by calculating and characterizing the X-ray absorption spectra of benzene and trifluoroacetonitrile at the time-dependent second-order algebraic diagrammatic construction level of theory.
关键词： time-dependent electronic structure calculations,X-ray absorption spectra,core-excited states,electronic wavepacket propagations,filter diagonalisation
更新于2025-09-23 15:21:01
-
Using density based indexes to characterize excited states evolution
摘要： With the aim of offering new computational tools helping in the description of photochemical reactions and phenomena occurring at the excited state, we present in this work the capability of a density based index (Π) in locating decay channels from higher to lower excited states. The Π index, previously applied to disclose non-radiative decay channels from the first excited state to the ground state, is very simple in its formulation and can be evaluated, practically with no extra computational cost, and coupled to any quantum method able to provide excited states densities. Indeed, this index relies only on the knowledge of energetics and electron densities of the different electronic states involved in the decay. In the present work, we show the proficiency of the Π index in the general case of decay between excited states by applying it to two model systems well characterized both theoretically and experimentally. In both cases, this descriptor was successful in spotting the regions where excited states are more likely to decay, thus suggesting its potential interest for further application in the design of new compounds.
关键词： density based indexes,excited states decay and crossing,funnel regions,quantum methods,photochemical reaction pathways
更新于2025-09-23 15:19:57
-
Evaluation of the quantum time-correlation functions employing the Hamilton–Jacobi dynamics framework
摘要： The quantum Hamilton–Jacobi equation (QHJE) is formally equivalent to the time-dependent Schr?dinger equation, and the solutions to the QHJE can be easily interpreted in terms of trajectories providing a link between classical and quantum mechanics. The trajectory-based approaches to quantum molecular dynamics are, generally, appealing because they circumvent exponential scaling associated with exact quantum methods with the system size, and because, unlike classical molecular dynamics, such methods incorporate dominant quantum effects due to delocalization of wavefunctions describing the nuclei. We explore the utility of the QHJE framework for calculations of the time-correlation functions (TCFs) involving quantum evolution defined by the Boltzmann density operator and by the Hamiltonian time-evolution operator. The implementation is based on solutions to the imaginary-time counterpart to the QHJE, which yield approximations to the ground state wavefunction. The resulting nodeless wavefunction is used to generate a basis in coordinate space, which is efficient for evaluation of the low-lying excited states and of the quantum TCFs, including the Kubo-transformed TCFs, at low temperature. The QHJE/basis approach is illustrated on several model systems in and out of thermal equilibrium, i.e., the H2 dimer and bound anharmonic potentials. If a system exhibits large amplitude motion, e.g., in case of the nonequilibrium dynamics, then the real-time trajectory propagation provides an alternative to the basis representation, as demonstrated on a model describing the inversion mode of the ammonia molecule and ion.
关键词： Trajectory dynamics,Time-correlation functions,Excited states,Quantum dynamics
更新于2025-09-23 15:19:57
-
Stimulated resonant inelastic x-ray scattering with chirped, broadband pulses
摘要： We present an approach for initiating and tracing ultrafast electron dynamics in core-excited atoms, molecules, and solids. The approach is based on stimulated resonant inelastic x-ray scattering induced by a single, chirped, broadband XUV or x-ray pulse. A first interaction with this pulse prepares a core-excited state wave packet by resonant core-excitation. A second interaction with the pulse at a later time induces the transition to valence-excited states, which is associated with stimulated emission. The preparation of the core-excited wave packet and the transition from the core-excited states to the valence-excited states occur at distinct chirp-dependent times. As a consequence, the stimulated emission carries information about the time evolution of the core-excited state wave packet.
关键词： XUV pulses,x-ray pulses,core-excited states,ultrafast electron dynamics,chirped pulses,stimulated resonant inelastic x-ray scattering
更新于2025-09-19 17:15:36
-
The characterization of electronic defect states of single and double carbon vacancies in graphene sheets using molecular density functional theory
摘要： A detailed picture of the electronic states manifolds of single- and double-vacancy defects in molecular models of graphene based on polycyclic aromatic hydrocarbons (PAHs) is presented. DFT calculations using various density functionals including long-range corrected ones have been performed for pyrene, circumpyrene and 7a,7z-periacene. It has been found for pyrene defect models that DFT results reproduced well the set of closely-spaced singlet and triplet states predicted by the CCSD(T) and previous MRCI + Q calculations, indicating the applicability of DFT for accessing the excited states manifolds also for larger graphene models. For the single-carbon vacancy defect, all structures have a triplet ground state. As expected, in the largest system, 7a,7z-periacene-1C, the lowest lying states are much closer in energy. For all double-vacancy defect structures, a significant rearrangement of the electronic states with increasing size of the sheet is observed. The closed-shell 1Ag state in the smallest systems is destabilised in the extended 7a,7z-periacene system, which has the 3B2u state as the ground state. As observed for the single-vacancy defect, the lowest lying states are closer in energy for the larger systems, since there are more π orbitals close in energy available. For all states, the formation of the bridging bonds for the double vacancy leads to distances shorter than for the single vacancy defect indicating a larger rigidity of the former structure which does not allow stronger distortions.
关键词： polycyclic aromatic hydrocarbons,Excited states,Periacenes,DFT,pyrene
更新于2025-09-19 17:15:36
-
Coupling of the First and Second Excited States of R6G Dye with the Fabry-Perot Cavity
摘要： Coupling of macroscopic ensembles of highly concentrated R6G molecules with aluminum and silver Fabry–Perot cavities of different sizes, in which one or two standing wave modes are in resonance with the absorption transition(s) of the dye molecules, have been studied. (i) It has been found that strong coupling of the cavity with one molecular eigenstate (S0!S1 transition) does not perturb the energies of the other molecular states. (ii) The S0!S2 absorption transition is too weak to strongly couple to the resonant cavity (“λ” standing wave mode). However, the resonant cavity causes a blue shift of the S0!S2 excitation band. (iii) The splitting of the dispersion curve is theoretically predicted and experimentally observed at strong coupling of the cavity resonance (“λ” standing wave mode) with the material resonances of Ag, including bound electron and “epsilon equal zero” transitions.
关键词： spectroscopy,Fabry–Perot cavity,energy splitting,excited states,spectral shifts,rhodamine 6G dye,strong coupling
更新于2025-09-19 17:15:36