We present herein a high-level ab initio study on the mono-iodine substituted carbene, CHI, using internally contracted multireference configuration interaction (icMRCI-F12) with Davidson correction which employs wave functions that explicitly depend on the electron–electron distance. The spin–orbit coupling (SOC) effect was included in our calculations. A total of 20 spin-free states with vertical transition energy up to 7.4 eV, as well as 50 spin-coupled states generated from the spin-free states via the SOC were studied. The results show significant influence of the SOC on the bond angles and the harmonic vibrational frequencies of the bending mode of the ground state (X1A′) and the lowest triplet state (a3A′′). Potential energy curves along the bond angle and the bond lengths of the electronic excited states of CHI were investigated. Based on our calculations, photodissociation dynamics in the ultraviolet region was disscussed for the first time, which would pave the way to further experimental investigations of CHI.

•The PECs of the 12 Λ-S states have been calculated.•The PDMs and SO matrix elements were computed.•The PECs of the 23 Ω states generated from 12 Λ-S states have been calculated.•The dipole-allowed transition properties are obtained for the first time.Ab initio calculations on low-lying electronic states of strontium hydride cations, SrH+, have been performed using the internally contracted multi-reference configuration interaction (icMRCI) method with Davidson correction (+ Q). Spin-orbit coupling (SOC) effect between the singlet and triplet states of SrH+ has been investigated for the first time. The potential energy curves (PECs) of a total of 12 Λ-S states, as well as the 23 Ω states generated from the Λ-S states after considering the SOC effect, have been calculated. The spectroscopic constants and transition properties, including the transition dipole moments, the Franck–Condon factors, and the radiative lifetimes, have been obtained based on the calculated PECs. It indicates that the SOC effect plays a non-negligible role in electronic states of SrH+. Our study should shed light on the structure and behavior of low-lying electronic states and should pave further experimental studies on the spectroscopy of strontium hydride cations.Figure: potential energy curves of singlet (solid lines) and triplet (dotted lines) Λ-S states of SrH+.Download high-res image (301KB)Download full-size image

•The PECs of the 24 electronic states have been calculated for the first time.•The ground state of AlO+ cation is determined to be the X1Σ+.•The predissociation mechanisms of the X1Σ+, A1Π, 21Σ+ states are analyzed.•The transition properties, TDMs, FCFs, and the radiative lifetimes are predicted.High-level ab initio calculations on the electronic states of AlO+ cation have been performed with the explicitly correlated multi-reference configuration interaction (MRCI-F12) method. The potential energy curves (PECs) of 24 electronic states have been obtained, most of which are reported for the first time. From the computed PECs, the precise spectroscopic constants of the bound states are determined. Our calculations confirm that the ground state of AlO+ cation is the X1Σ+ state. The permanent dipole moments (PDMs) functions of the selected bound states are computed. The spin–orbit (SO) matrix elements between the electronic states involved in the crossing region of the PECs are calculated to analyze the predissociation mechanisms of the X1Σ+, A1Π, and 21Σ+ states. Finally, the transition properties of four spin-allowed transitions are predicted, including the transition dipole moments (TDMs), Franck-Condon Factors (FCFs), and the radiative lifetimes. This work should enhance our understanding on the electronic structure and spectroscopy of AlO+ cation.The crossing regions of the PECs.Download high-res image (143KB)Download full-size image

•A total of 60 isomers of C6H5+ cations were obtained at density functional theory.•The stability and isomerization reactions of C6H5+ isomers were performed.•The structures, frequencies, thermodynamic properties of isomers were summarized.•Ring to ring or chain isomerization pathways were investigated using IRC method.•Result shows reactions contain hydrogen transfer, bond broken and reconstruction.As a key polyatomic molecular cation that plays a pivotal role in growth of the polycyclic aromatic hydrocarbons, phenyl cation C6H5+ exhibits various isomers and isomerization reactions. Investigation on the structure and stability of the isomers as well as the isomerization is important for better understanding the chemical reactions involving C6H5+ cations. In this work, we have performed a theoretical study on the stability and isomerization reactions of C6H5+ isomers at density functional theory B3LYP/6-311G (d, p) level. We have obtained a total of 60 isomers of C6H5+ cations, most of which are reported for the first time. The geometries, vibrational frequencies, thermodynamic properties and stability of 28 out of 60 isomers have been summarized in detail. Different ring-to-ring and ring-to-chain isomerization pathways, which are connected via 28 transition states, have been investigated using the intrinsic reaction coordinate method. The results show that the isomerization reactions occur via hydrogen migration followed by bond-breaking and reconstruction.

High-level ab initio calculations on the ground and the excited states of aluminum monobromide (AlBr) have been carried out by utilizing the internally contracted multireference configuration interaction method plus Davidson correction (icMRCI+Q) method. The core–valence correlation (CV) correction and spin–orbit coupling (SOC) effect have been investigated in the calculations. The potential energy curves (PECs) of the 13 Λ–S states, as well as those of the 24 Ω states generated from the Λ–S states under the SOC effect, have been obtained. The spectroscopic constants of the bound states have been determined, which are in accordance with the available experiment results. The SOC induced predissociation mechanisms of the a3Π and A1Π states have been analyzed with the aid of the spin–orbit matrix element. The transition properties of 0+(2)-X0+, 1(1)-X0+ and 1(2)-X0+ transitions are predicted, including the transition dipole moments (TDMs), Franck–Condon factors (FCFs), and the radiative lifetimes. Finally, the possibility of AlBr to be used for molecular laser cooling has been discussed based on our calculations.

•The PECs of the 7 Λ–S states have been calculated.•The non-adiabatic couplings of the Λ–S states have been calculated.•The PDMs and SO matrix elements were computed to reveal the sudden changes at RACP.•The PECs of the 12 Ω states generated from 7 Λ–S states have been calculated.•The abrupt changes have been explained with the wavefunctions.A high-level ab initio calculation on the ZnH+ cation has been carried out with the multi-reference configuration interaction method plus Davison correction (MRCI + Q). The scalar relativistic effect is included by using the Douglas–Kroll–Hess (DKH) method. The calculated potential energy curves (PECs) of the 7 Λ–S states are associated with the dissociation limits of Zn+(2Sg) + H(2Sg), Zn(1Sg) + H+(1Sg), and Zn+(2Pu) + H(2Sg), respectively (The Λ–S state is labeled as 2S + 1Λ, in which Λ is the quantum number for the projection along the internuclear axis of the total electronic orbital angular momentum and S is the total electron spin). The spectroscopic constants of the bound states are determined and in good agreement with the available theoretical and experimental results. The permanent dipole moments (PDMs) of Λ–S states and the spin–orbit (SO) matrix elements between Λ–S states are also computed. The results show that the abrupt changes of the PDMs and SO matrix elements come into being for the reason of the avoided crossing between the states with the same symmetry. In addition, the non-adiabatic couplings matrix elements between Λ–S states are also evaluated. Finally, the spin–orbit couplings (SOCs) for the low-lying states are considered with Breit-Pauli operator. The SOC effect makes the 7 Λ–S states of the ZnH+ cation split into 12 Ω states (Ω = Λ + Sz, in which Sz is projection of the total electron spin S along the internuclear Z-axis). For the (3)0+ state, the two energy minima exhibit in the potential, which could be attributed to the formation of the new avoided crossing point. The transition dipole moments (TDMs), Franck–Condon factors, and the radiative lifetimes of the selected transitions (2)0+-X0+, (3)0+-X0+, (2)1-X0+ and (3)1-X0+ have been reported.The permanent dipole moment of the Λ–S states.

•The PECs of the 22 Λ–S states have been calculated.•The metastable state a1Δ has been studied for the first time.•The PECs of the 51 Ω states arising from 22 Λ–S states have been calculated.•The perturbations between the states have been studied with SO matrix elements.•The coupling among the Λ-S states have been analyzed with Ω-state wavefunctions.The potential energy curves (PECs) of the 22 Λ–S states of the phosphorus monoiodide (PI) molecule have been calculated at the level of MRCI+Q method with correlation-consistent quadruple-ζ quality basis set. The spectroscopic constants of the bound states are determined, which well reproduce the available measurements. The metastable a1Δ state has been reported for the first time, which lies between the X3Σ− and b1Σ+ states and have much deeper well than the ground state. The R-dependent spin–orbit (SO) matrix elements are calculated with the full-electron Breit–Pauli operator. Based on the SO matrix elements, the perturbations that the 23Π state may suffer from are analyzed in detail. The SOC effect makes the original Λ–S states split into 51 Ω states. In the zero-field splitting of the ground state X3Σ−, the spin–spin coupling contribution (2.23 cm−1) is found to be much smaller compared to the spin–orbit coupling contribution (50 cm−1). The avoided crossings between the Ω states lead to much shallower potential wells and the change of dissociation relationships of the states. The Ω-state wavefunctions are analyzed depending on their Λ–S compositions, showing the strong interactions among several quasidegenerate Λ–S states of the same total SO symmetry. The transition properties including electric dipole (E1), magnetic dipole (M1), and electric quadrupole (E2) transition moments (TMs), the Franck–Condon factors, the transition probabilities and the radiative lifetimes are computed for the transitions between Ω components of a1Δ and b1Σ+ states and ground state. The transition probabilities induced by the E1, E2, and M1 transitions are evaluated. The E2 makes little effect on transition probabilities. In contrast, the E1 transition makes the main contribution to the transition probability and the M1 transition also brings the influence that cannot be neglected. Finally, the radiative lifetimes are determined with the transition moments including E1 and M1. The lifetime of transition (2)0+–X10+ is evaluated at the level of millisecond, much smaller than that of the transition (2)0+–X21.

•Interaction of CO2/CS2/OCS with strong 800/400 nm lasers was studied using TOF-MS.•Each ion yield vs laser intensity and polarization was measured at both wavelengths.•Mechanism of strong-field single/double ionization and fragmentation was discussed.Ionization of molecules in strong femtosecond laser fields is a key process for understanding a variety of strong-field molecular physical phenomena. In this study, we performed an experimental study on strong-field ionization and dissociation of three linear triatomic molecules, CO2, CS2, and OCS, using time-of-flight mass spectrometer. We measured the yield of different parent ions and various fragment ions as a function of laser intensity in the range of 2.0 × 1013 W/cm2 to 8.0 × 1014 W/cm2, in both 800-nm and 400-nm strong laser fields. The mechanism of strong-field single and double ionization, as well as fragmentation, was discussed based on the experimental results. In addition, the angular distributions of fragment ions were obtained. The results show the anisotropic distributions in the formation of highly charged atomic fragment ions, which may be attributed to the alignment of the molecules in strong laser fields before dissociation.

We present herein a high-level ab initio study on the electronic excited states of CHCl using the internally contracted multireference configuration interaction method including Davidson correction (icMRCI+Q). A total of 13 electronic states with energy of up to 7 eV have been investigated. The vertical transition energies, oscillator strengths, electron configurations, and transitions of the electronic states of CHCl have been calculated at the icMRCI+Q/aug-cc-pv(5+d)Z level. The potential energy curves of the electronic states have been studied along the H–C–Cl angle, the C–H bond length, and the C–Cl bond length, respectively. Our theoretical study has provided comprehensive information for understanding the interaction and the behavior of the electronic excited states of CHCl. In particular, the excited state involved in the 193 nm photodissociation as well as the corresponding dissociation dynamics have been discussed on the basis of our calculation results. The present study should shed more light on the photochemistry of CHCl in the ultraviolet region.

•The PECs of GeH were computed with the MRCI method.•The spin–orbit coupling effect was considered in the calculations.•The spectroscopic constants of Λ–S and Ω states of GeH were fitted.•The predissociation mechanisms of A2Δ, 22Σ+ and 32Σ+ states were discussed.•The radiative lifetimes of A2Δ and a4Σ− states of GeH were evaluated.Germanium monohydride (GeH), an important radical for the growth of semiconductor germanium film, has received much attention. However, the electronic structure and spectroscopic properties of low-lying excited states of the radical have not been well understood, especially the coupling between different electronic states. In this work, eight Λ–S valence states and four low-lying Λ–S Rydberg states correlated to the four lowest dissociation limits of GeH are investigated by employing the multireference configuration interaction method. With the inclusion of spin–orbit coupling effect, there are 24 Ω states generated from 12 Λ–S states. On the basis of computed potential energy curves of the Λ–S and Ω states, the spectroscopic parameters of bound states are evaluated, which demonstrate that the first Rydberg state 32Σ+ located at 5.12 eV is exactly the B2Σ+ state tentatively assigned by experiment. With the help of the calculated spin–orbit matrix elements, the predissociation mechanism of A2Δ state is investigated, which may interpret the fact that ν′>2 vibrational levels of A2Δ state are difficult to be detected in experiment. Finally, the transition dipole moments and the radiative lifetimes of several vibrational levels of A2Δ and a4Σ− states are calculated.

•MRCI+Q calculations were carried out for the excited states of CdH.•Effect of spin–orbit coupling was included in the calculations.•Spectroscopic constants of bound Λ-S and Ω states of CdH were evaluated.•Predissociation mechanisms of C2Σ+, 42Σ+ and 22Π states were discussed.•Radiative lifetimes of A2Π, B2Σ+ and C2Σ+states of CdH were calculated.We calculated the potential energy curves of 10 Λ-S states correlated with the five lowest dissociation limits of the CdH radical by a configuration interaction method, as well as those of 17 Ω states generated from the Λ-S states. The spectroscopic parameters of bound states were calculated and found to be well consistent with the latest experimental results. We also discussed the possible predissociation mechanisms of C2Σ+, 42Σ+ and 22Π states on the basis of the calculation of spin–orbit elements. Finally, the allowed transition dipole moments and the radiative lifetimes of A2Π, B2Σ+ and C2Σ+ states were obtained.Graphical abstract

•The excited states of GeH+ were calculated with MRCI + Q method.•The spin–orbit coupling effect was taken into account in the calculations.•Spectroscopic constants of bound Λ-S and Ω states of GeH+ were computed.•The radiative lifetimes of A1Π1, a3Π0+, and a3Π1 states of GeH+ were obtained.High level calculations using configuration interaction method have been carried out for 8 Λ-S states correlated to the two lowest dissociation limits of GeH+. The spin–orbit coupling, core-valence correlation and scalar relativistic effects were included. The potential energy curves of 8 Λ-S states as well as 23 Ω states generated from the 8 Λ-S states were given. The spectroscopic parameters of the bound states were obtained, which agree well with available experimental results. Finally, the transition dipole moments as well as the radiative lifetimes of three lowest vibrational states of A1Π1, a3Π0+, and a3Π1 states were evaluated.

•The electronic states of BrF and BrF+ were calculated with spin–orbit CI method.•Spectroscopic constants for bound states of BrF and BrF+ were obtained.•The adiabatic and vertical ionization energies of BrF were computed.Bromine monofluoride (BrF) and its cation (BrF+) have attracted much scientific attention because of their potential significance in the stratospheric ozone depletion and the development of chemical laser. Despite that the structure and spectroscopic properties of the 13Π0+ (B3Π0+) and 13Π1 states of BrF have been experimentally investigated in the literature, theoretical investigations of BrF and its cation are relatively sparse. In this paper, the low-lying electronic states for BrF/BrF+ were studied by means of relativistic multireference configuration interaction method (including Davidson correction). The spin–orbit coupling effect was considered by the state-interacting method with the full Breit-Pauli Hamiltonian. For BrF, the potential energy curves (PECs) of 12 Λ–S states and 23 Ω states generated from the Λ–S states were calculated. The avoided crossing mechanism of Ω = 0+ states were analyzed by the variations of dominant Λ–S composition for Ω states at several different internuclear distances. For BrF+, the PECs of the ground states (X2Π3/2 and X2Π1/2) were computed. The spectroscopic constants of the bound states of BrF/BrF+ were determined, which are in good agreement with previously available experimental results. Finally, the ionization energies from the neutral ground state (X1Σ+) to different ionic states (X2Π3/2, and X2Π1/2) were obtained.

We present herein the first all-electron relativistic internally contracted multireference configuration interaction with Davidson correction (icMRCI+Q) study on the low-lying states of fluoroiodo carbene, CFI, which contains the most electronegative element (fluorine) and the heavy halogen (iodine). The potential energy surface (PES) of the first excited singlet state (Ã1A″) of CFI was carefully examined along the C–I bond distance at the icMRCI+Q/ANO-RCC level, while the other two geometric parameters were optimized at every C–I bond length in contrast to fixing them at the equilibrium values. A reliable barrier height of the Ã1A″ state was determined to be 625 cm–1 by our high-level icMRCI+Q calculations with large ANO-RCC basis set and with inclusion of the spin–orbit coupling, core–valence correlation, and zero-point-energy. Finally, the electronic states of CFI with vertical transition energy up to 6 eV were studied. The calculation presented here will provide more comprehensive results about the structure and behavior of electronic states of CFI radical.

In this work, we performed a high level ab initio study on the low-lying electronic states of CSe, utilizing MRCI+Q (the internally contracted multireference configuration interaction, and Davidson’s correction) method with scalar relativistic and spin–orbit coupling effects taken into account. The potential energy curves of 18 Λ–S states associated with the lowest dissociation limit of CSe molecule, as well as those of 50 Ω states generated from the Λ–S states were computed. The spectroscopic parameters of bound states were evaluated, which agree well with existing theoretical and experimental results. With the aid of calculated spin–orbit matrix elements and the Λ–S compositional variation of the Ω states, the spin–orbit perturbations of low-lying states to the A1Π and a3Π states are analyzed. Finally, the transition dipole moments of A1Π, A′1Σ+, a3Π0+, and a3Π1 to the ground X1Σ+ state as well as the lifetimes of the four excited states were evaluated.

Carbon monosulfide (CS), which plays an important role in a variety of research fields, has long received considerable interest. Due to its transient nature and large state density, the electronic states of CS have not been well understood, especially the interactions between different states. In this paper, we performed a detail ab initio study on the low-lying electronic states of CS by means of the internally contracted multireference configuration interaction method (including Davidson correction) with scalar relativistic correction using the Douglas–Kroll–Hess Hamiltonian. We focused on the spin–orbit coupling of the states via the state interaction method with the full Breit–Pauli Hamiltonian. The potential energy curves (PECs) of 18 Λ–S states correlated with the lowest dissociation limit of the CS molecule were calculated, as well as those of 50 Ω states generated from the Λ–S states. The spectroscopic constants of the bound states were obtained, which are in good agreement with previous available experimental and theoretical results. The state perturbations of the a3Π and A1Π states with other low-lying electronic states are discussed in detail, based on the calculated spin–orbit matrix as well as the PECs of the Ω states. Avoided crossing in the states of CS was indicated when spin–orbit coupling was taken into account. Finally, the allowed transition dipole moments as well as the lifetimes of the five lowest vibrational states of the A1Π1, A′1Σ+0+ and a3Πi states were obtained.

Fluorobromo carbene, an important halogenated carbene in the stratospheric ozone depletion, has long been received considerable interest. However, the energy, structure, and dynamics of even the lowest excited states have not been well understood. In this paper, we performed a detail ab initio study on CFBr using complete active space second-order perturbation (CASPT2) and multireference configuration interaction (MRCI) method. We investigated the effect of basis set on the CASPT2 results of the ground X1A′ state and the first excited singlet A1A″ state. The potential energy surface (PES) of the A1A″ state along C–Br bond distance was carefully examined at CASPT2/cc-pV5Z level, by optimizing C–F bond and F–C–Br angle at every C–Br bond length in contrast to fix them at the equilibrium values. On the basis of the PES, a reliable barrier height of the A1A″ state was obtained from CASPT2 and MRCI+Q calculations with different basis sets, considering the scalar relativistic effect, spin–orbit coupling, and core–valence correlation. Finally, we carried out the first theoretical study on higher excited state with energy up to 7 eV. The present calculated results were compared with previous experimental and theoretical results where available. Our results will add some understanding and shed more light on the structure and dynamics of electronic states of CFBr radical.

The ultrafast dynamics and dissociative ionization of CS2 were studied using the pump-probe method with time-of-flight mass spectroscopy. The transient behavior of both parent ion (CS2+) and fragment ions (S+ and CS+) was observed. It was found that all the ionic signals decay exponentially with lifetimes that were different for delay times, t>0 and t<0, which can be attributed to the evolution of different Rydberg states pumped by 267-nm and 400-nm laser pulses. The lifetimes of two Rydberg states were obtained simultaneously from one fitting of the transients. The fragment ions were produced by the dissociation of CS2+, and it is suggested that the final ionic state is the C2Σg+ state of CS2+ based on the measured S+/CS+ branching ratio. The S+/CS+ ratio is dependent on the delay time of the two lasers, indicating that the dissociation process of CS2+ is related to the evolution of the intermediate Rydberg state.

A novel method for monitoring of enzyme reaction and inhibition with high temporal resolution was developed by using optically gated vacancy capillary electrophoresis (OGVCE) with laser-induced fluorescence (LIF) detection and immobilized enzyme. Trypsin cleavage reaction and inhibition were investigated by the presented OGVCE-LIF assay, using carboxyfluorescein (FAM) end-labeled Angiotensin as the substrate and commercially available immobilized trypsin. The substrate and the product were continuously loaded into the capillary by the electroosmotic flow while the immobilized enzyme remained in the sample vial. Substrate consumption and product formation were monitored simultaneously at 5 s interval during the whole reaction time. The enzymatic reaction rates obtained from the substrate and the product were highly consistent. The enzyme activity and the Michaelis constants of trypsin cleavage reaction, as well as the inhibition constant (for reversible competitive inhibitor) and the inhibition fraction (for irreversible inhibitor), were obtained. It was showed that the reported OGVCE-LIF method can perform fast, accurate, sensitive and reproducible CE enzyme assay with high temporal resolution, thus has great potential in application of the enzyme-substrate systems with fast reaction rate and the fluorescent substrate and products.

We present herein a high-level ab initio study on the mono-iodine substituted carbene, CHI, using internally contracted multireference configuration interaction (icMRCI-F12) with Davidson correction which employs wave functions that explicitly depend on the electron–electron distance. The spin–orbit coupling (SOC) effect was included in our calculations. A total of 20 spin-free states with vertical transition energy up to 7.4 eV, as well as 50 spin-coupled states generated from the spin-free states via the SOC were studied. The results show significant influence of the SOC on the bond angles and the harmonic vibrational frequencies of the bending mode of the ground state (X1A′) and the lowest triplet state (a3A′′). Potential energy curves along the bond angle and the bond lengths of the electronic excited states of CHI were investigated. Based on our calculations, photodissociation dynamics in the ultraviolet region was disscussed for the first time, which would pave the way to further experimental investigations of CHI.