Spectroscopy and molecule opacity investigation on excited states of SiS

The SiS molecule,which plays a significant role in space,has attracted a great deal of attention for many years.Due to complex interactions among its low-lying electronic states,precise information regarding the molecular structure of SiS is limited.To obtain accurate information about the structure of its excited states,the high-precision multireference configuration interaction(MRCI)method has been utilized.This method is used to calculate the potential energy curves(PECs)of the 18Λ–S states corresponding to the lowest dissociation limit of SiS.The core–valence correlation effect,Davidson’s correction and the scalar relativistic effect are also included to guarantee the precision of the MRCI calculation.Based on the calculated PECs,the spectroscopic constants of quasi-bound and bound electronic states are calculated and they are in accordance with previous experimental results.The transition dipole moments(TDMs)and dipole moments(DMs)are determined by the MRCI method.In addition,the abrupt variations of the DMs for the 1^(5)Σ^(+)and 2^(5)Σ^(+)states at the avoided crossing point are attributed to the variation of the electronic configuration.The opacity of SiS at a pressure of 100 atms is presented across a series of temperatures.With increasing temperature,the expanding population of excited states blurs the band boundaries.

Excitation and ionization of OCS molecules in strong UV and NIR laser fields

Rydberg state excitation(RSE) is a highly non-linear physical phenomenon that is induced by the ionization of atoms or molecules in strong femtosecond laser fields. Here we observe that both parent and fragments(S, C, OC) of the triatomic molecule carbonyl sulfide(OCS) can survive strong 800 nm or 400 nm laser fields in high Rydberg states. The dependence of parent and fragment RSE yields on laser intensity and ellipticity is investigated in both laser fields, and the results are compared with those for strong-field ionization. Distinctly different tendencies for laser intensity and ellipticity are observed for fragment RSE compared with the corresponding ions. The mechanisms of RSE and strong-field ionization of OCS molecules in different laser fields are discussed based on the experimental results. Our study sheds some light on the strong-field excitation and ionization of molecules irradiated by femtosecond NIR and UV laser fields.

Core level excitation spectra of La and Mn ions in LaMnO3

Manganese-based perovskite is popular for research on ferromagnetic materials,and its spectroscopic studies are essential for understanding its electronic structure,dielectric,electrical,and magnetic properties.In this paper,the M-edge spectra of La ions and the M-edge,L-edge,and K-edge spectra of Mn ions in LaMnO3 are calculated by considering both the free-ion multiplet calculation and the crystal field effects.We analyze spectral shapes,identify peak origins,and estimate the oxidation states of La and Mn ions in LaMnO3 theoretically.It is concluded that La ions in LaMnO3 predominantly exist in the trivalent state,while Mn ions exist primarily in the trivalent state with a minor presence of tetravalent ions.Furthermore,the calculated spectra are in better conformity with the experimental spectra when the proportion of Mn3+is 90%and Mn4+is 10%.This article enhances our comprehension of the oxidation states of La and Mn within the crystal and also provides a valuable guidance for spectroscopic investigations of other manganates.

Even-parity states of the Sm atom with stepwise excitation

Two-colour stepwise excitation and photoionization schemes are adopted to study the spectra of high-lying states of the Sm atom. These bound even-parity states are excited with three different excitation paths from the 4f66s6p7DJ （J = 1, 2, 3） intermediate states, respectively. They are probed by photoionization process with an extra photon driving them to the continuum states. In this experiment, 270 states are detected in an energy range from 36160 cm-1 to 42250 cm-1, 109 of which are newly discovered, while the rest of them are confirmed to be the energy levels reported previously. Furthermore, based on the J-momentum selection rules of three excitation paths, a unique assignment of J-momentum for all observed states is determined, eliminating all remaining ambiguities in the literature. Finally, 53 single-colour transitions originating from the scanning laser are also identified. For all the relevant transitions, the information about their relative intensities is also given in the paper.

Two-proton radioactivity from excited states of proton-rich nuclei within Coulomb and Proximity Potential Model

In the present work,we extend the Coulomb and Proximity Potential Model(CPPM)to study two-proton(2p)radioactivity from excited states while the proximity potential is chosen as AW95 proposed by Aage Withner in 1995.Demonstration reveals that the theoretical results acquired by CPPM exhibit a high level of consistency with prior theoretical models such as the unified fission model(UFM),generalized liquid-drop model(GLDM)and effective liquid-drop model(ELDM).Furthermore,within the CPPM,we predicted the half-lives of potential 2p radioactive nuclei for which experimental data are currently unavailable.The predicted results were then assessed,compared with UFM,ELDM and GLDM models,and examined in detail.

Role of excited states in helium-like ions on high-order harmonic generation

We theoretically investigate high-order harmonic generation(HHG) of helium(He), lithium cation(Li+), and beryllium dication(Be2+) using the time-dependent Hartree–Fock method to solve the three-dimensional time-dependent Schr ¨odinger equation. It is found that the intensity of the HHG increases significantly from a certain harmonic order below the ionization threshold, and the initial position of the enhancement does not depend on the intensity or the wavelength of the driving laser field. Further analysis shows that excited states play an important role on this enhancement,consistent with the excited-state tunneling mechanism [Phys. Rev. Lett. 116 123901(2016)]. Our results unambiguously show that excited-state tunneling is essential for understanding the enhancement of HHG. Accordingly, a four-step model is herein proposed to illustrate the multiphoton excitation effect in helium-like ions, which enriches the physics of HHG enhancement.

A TD-DFT Study for the Excited State Calculations of Microhydration of N-Acetyl-Phenylalaninylamide (NAPA)

Investigating the impact of microhydration on the excited-states and electronic excitation properties of biomolecules has remained one of the important yet challenging aspects of science because of the complexity of developing models. However, with the advent of computational chemistry methods such as TD-DFT, many useful insights about the electronic excitation energy and excited-state nature of biomolecules can be explored. Accordingly, in our study, we have incorporated the TD-DFT/wB97XD/cc-pVTZ method to study the excited state properties of N-acetyl phenylalanine amide (NAPA-A(H2O) n) (n = 1 to 4) clusters from ground to the tenth lowest gaseous singlet excited state. We found that the C=O bond length gradually increases both in N-terminal amide and C-terminal amide after the sequential addition of water molecules because of intermolecular H-bonding and this intermolecular H-bonding becomes weaker after the sequential addition of H2O molecules. The UV absorption maxima of NAPA-A (H2O)n (n = 1 - 4) clusters consisted of two peaks that are S5←S0 (1st absorption) and S6←S0 (2nd absorption) excitations. The first absorption maxima were blue-shifted with the increase in oscillator strength. This means that strong H-bonds reduce the charge transfer and make clusters more rigid. On the other hand, the second absorption maxima were red-shifted with the decrease in oscillator strength. In the ECD spectra, the negative bands indicate the presence of an amide bond and L-configuration of micro hydrated NAPA-A clusters. Finally, our calculated absorption and fluorescence energy confirm that all the NAPA-A (H2O) n (n = 0 - 4) clusters revert to the ground state from the fluorescent state by emitting around 5.490 eV of light.

Atomic N00N state generation in distant cavities by virtual excitations

A general scheme of generating NOON states of virtually-excited 2N atoms is proposed. The two cavities are fibre-connected with N atoms in each cavity. Although we focus on the case of N = 2, the system can be extended to a few atoms with N 〉2. It is found that all 2N atoms can be entangled in the form of NOON states if the atoms in the first cavity are initially in the excited states and atoms in the second cavity are all in the ground states. The feasibility of the scheme is carefully discussed, it shows that the NOON state with a few atoms can be generated with good fidelity and the scheme is feasible in experiment.

Generation of Multi-mode Entangled Coherent States for N Trapped Ions in Strong-Excitation Regime

We propose a scheme to generate entangled coherent states for the vibrational modes of N trapped ions.In the scheme the first ion is sequentially excited by two travelling wave laser fields tuned to the ion transition. The scheme works in the strong-excitation regime, which is of experimental importance in view of decoherence.

Electron excitation from ground state to first excited state:Bohmian mechanics method

The excitation process of electrons from the ground state to the first excited state via the resonant laser pulse is investigated by the Bohmian mechanics method. It is found that the Bohmian particles far away from the nucleus are easier to be excited and are excited firstly, while the Bohmian particles in the ground state is subject to a strong quantum force at a certain moment, being excited, to the first excited state instantaneously. A detailed analysis for one of the trajectories is made, and finally we present the space and energy distribution of 2000 Bohmian particles at several typical instants and analyze their dynamical process at these moments.

Two-Variable Hermite Polynomial Excitation of Two-Mode Squeezed Vacuum State as Squeezed Two-Mode Number State

We find that the squeezed two-mode number state is just a two-variable Hermite polynomial excitation of thetwo-mode squeezed vacuum state (THPES).We find that the Wigner function of THPES and its marginal distributionsare just related to two-variable Hermite polynomials (or Laguerre polynomials) and that the tomogram of THPES canbe expressed by one-mode Hermite polynomial.

Temporal electronic structure of non-resonant Raman excited virtual state of P-nitroaniline by 514 nm excitation via bond polarisabilities

We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al. in 1987 （Tian B, Wu G, Liu G 1987 J. Chem. Phys. 87 7300）. The bond polarisabilities provide much information concerning the electronic structure of the non-resonant Raman excited virtual state. At the initial moment by the 514.5 nm excitation, the tendency of the excited electrons （mapped out by the bond polarisabilities） is to spread to the molecular periphery, and the electronic structure of the Raman virtual state is close to the pseudoquinonoidic state. When the final stage of relaxation is approached, the bond polarisabilities of those peripheral bonds relax faster than those closer to the molecular core, the phenyl ring. The molecule is in the benzenoidic form as demonstrated by the bond polarisabilities after relaxation.

Excitation Halo States of ^(12)B

Angular distributions for the ^(11)B(d,p)^(12)B transfer reactions have been measured at E_(1ab) = 11.8 Me V. The asymp-totic normalization coefficients (ANC) of the ground state, the second and third excitation states for ^(12)B(^(11)B+n) are extracted from the differential cross sections at three forward angles. With these ANCs, the root-mean-square radii are calculated for these three states. The results show that the second and third excitation states of ^(12)B are neutron halo states.

Atomic GHZ States Prepared in Two Directly Coupled Cavities with Virtual Excitations in One Step

A scheme for one-step preparation of atomic GHZ states in two directly coupled cavities via virtual excitations is proposed.In the whole procedure,the information is carried only in two ground states of A-type atoms, while the excited states of atoms and cavity modes are virtually excited,leading the system to be insensitive to atomic spontaneous emission and photon loss.

Behaviours of the excited states 1s^2 np along lithium isoelectronic sequence from Z=11 to 20

Based on the obtained energy values of 1s^2np （n≤ 9） states for lithium-like systems from Z=11 to 20 （by the authors of this paper： Hu M H and Wang Z W 2004 Chin. Phys. 13 662）, this paper determines the quantum defects, as slowly varying function of energy, of this Rydberg series. Using them as input, it can predict the energies of any highly excited states below the ionization threshold for this series a^cording to the quantum defect theory. The regularities of variation for quantum defects of the series along this isoelectronic sequence are physically analysed and discussed. The screening parameters, which are equal to the effective screening charge of the core-electrons, are also obtained.

Study of the excitation properties of the Si_3 O_2 cluster under an external electric field

The structure of the Si3Ox （x =2, 3） cluster is investigated; we find that the geometry of Si3O2 is similar to that of Si3O3 except for the oxygen-deficient defect structure （Si-Si band） which exists only in the Si3O2 cluster. It is known that oxygen-deficient defects are used to explain visible luminescence （especially blue, purple and ultraviolet light） from silicon-based materials, which are directly bound up with the excited states of the molecules. Therefore the excitation properties of the two clusters are also studied. Our results show that the absorption spectrum of Si3O2 is concentrated in the visible light region. In contrast, the absorption spectrum of Si3O3 is mainly located in the ultraviolet light region. The calculations are perfectly consistent with experimental data and also support the theory of oxygen-deficient defects.

Effects of three-body interaction on collective excitation and stability of Bose-Einstein condensate

This paper investigates the collective excitation and stability of low-dimensional Bose-Einstein condensates with two- and three-body interactions by the variational analysis of the time-dependent Gross-Pitaevskii-Ginsburg equation. The spectrum of the low-energy excitation and the effective potential for the width of the condensate axe obtained. The results show that： （i） the repulsive two-body interaction among atoms makes the frequency red-shifted for the internal excitation and the repulsive or attractive three-body interaction always makes it blue-shifted; （ii） the region for the existence of the stable bound states is obtained by identifying the critical value of the two- and three-body interactions.

Neutron Halos in the Excited States of Spherical Nuclei Near the β-Stable Line

The newly discovered neutron halos in the excited states of nuclei 12B, 13C, and 209pb are studied by therelativistic mean-field theory. The calculated binding energies are very close to the experimental ones. The experimentally extracted root-mean-square radii of the last neutron with different occupations in nuclei are well reproduced bycalculations. New candidates for the neutron halos in excited states are predicted and are useful for further search ofneutron halos in the excited states of stable nuclei.

Role of excited states in the elliptically polarized harmonic generation

We theoretically investigate the contribution of the excited state to the ellipticity of the harmonics from H＋ at different orientation angles irradiated by a linearly polarized laser pulse. It is found that the first excited state has a significant influence to the ellipticity of the harmonics, and the contribution of higher excited states to the ellipticity can be neglected. Moreover, the conclusion is not dependent on the laser intensity.

Time-dependent Density Functional Theory Study on the Electronically Excited States of N-Methylformamide in Aqueous Solution

Excited-state hydrogen-bonding dynamics of N-methylformamide （NMF） in water has been investigated by time-dependent density functional theory （TDDFT） method. The ground-state geometry optimizations were calculated by density functional theory （DFT） method, while the electronic transition energies and corresponding oscillation strengths of the low-lying electronically excited states of isolated NMF, water monomers and the hydrogen-bonded NMF-H 2 O were calculated by TDDFT method. According to Zhao＇s rule on the excited-state hydrogen bonding dynamics, our results demonstrate that the intermolecular hydrogen bond C=O···O-H is strengthened and weakened in different electronically excited states. The hydrogen bond strengthening and weakening in the electronically excited state plays an important role in the photophysics of NMF in solutions.