6,740 research outputs found
Franck-Condon simulation of the single-vibronic-level emission spectra of HPCI/DPCl and the chemiluminescence spectrum of HPCI, including anharmonicity
No full textRestricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] potential energy functions (PEFs) were calculated for the (X) over tilde (2)A" and (A) over tilde (2)A'states of HPCl employing the augmented correlation-consistent polarized-valence-quadruple-zeta (aug-cc-pVQZ) basis set. Further geometry optimization calculations were carried out on both electronic states of HPCl at the RCCSD(T) level with all electron and quasirelativistic effective core potential basis sets of better than the aug-cc-pVQZ quality, and also including some core electrons, in order to obtain more reliable geometrical parameters and relative electronic energy of the two states. Anharmonic vibrational wave functions of the two states of HPCl and DPCl, and Franck-Condon (FC) factors of the (A) over tilde (2)A'-(X) over tilde (2)A" transition were computed employing the RCCSD(T)/aug-cc-pVQZ PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the single-vibronic-level (SVL) emission spectra of HPCl and DPCl reported by Brandon et al. [J. Chem. Phys. 119, 2037 (2003)] and the chemiluminescence spectrum reported by Bramwell et al. [Chem. Phys. Lett. 331, 483 (2000)]. Comparison between simulated and observed SVL emission spectra gives the experimentally derived equilibrium geometry of the (A) over tilde (2)A' state of HPCl of r(e)(PCI)=2.0035 +/- 0.0015 Angstrom, theta(e) = 116.08 +/- 0.60degrees, and r(e)(HP) = 1.4063 +/- 0.0015 Angstrom via the iterative Franck-Condon analysis procedure. Comparison between simulated and observed chemiluminescence spectra confirms that the vibrational population distribution of the (A) over tilde (2)A' state-of HPCl is non-Boltzmann, as proposed by Baraille, et al. [Chem. Phy. 289, 263 (2003)]
Ab initio calculations on SF2 and its low-lying cationic states: Anharmonic Franck-Condon simulation of the uv photoelectron spectrum of SF2
No full textGeometry optimization calculations were carried out on the X (1)A(1) state of SF2 and the X B-2(1), A (2)A(1), B B-2(2), C B-2(2), D (2)A(1), and E (2)A(2) states of SF2+ employing the restricted-spin coupled-cluster single-double plus perturbative triple excitation [RCCSD(T)] method and basis sets of up to the augmented correlation-consistent polarized quintuple-zeta [aug-cc-pV(5+d)Z] quality. Effects of core electron (S 2s(2)2p(6) and F 1s(2) electrons) correlation and basis set extension to the complete basis set limit on the computed minimum-energy geometries and relative electronic energies (adiabatic and vertical ionization energies) were investigated. RCCSD(T) potential energy functions (PEFs) were calculated for the X (1)A(1) state of SF2 and the low-lying states of SF2+ listed above employing the aug-cc-pV(5+d)Z and aug-cc-pV5Z basis sets for S and F, respectively. Anharmonic vibrational wave functions of these neutral and cationic states of SF2, and Franck-Condon (FC) factors of the lowest four one-electron allowed neutral photoionizations were computed employing the RCCSD(T) PEFs. Calculated FC factors with allowance for Duschinsky rotation and anharmonicity were used to simulate the first four photoelectron bands of SF2. The agreement between the simulated and observed first bands in the He I photoelectron spectrum reported by de Leeuw [Chem. Phys. 34, 287 (1978)] is excellent. Our calculations largely support assignments made by de Leeuw on the higher ionization energy bands of SF2
The singlet-triplet separation in CF2: state-of-the-art ab initio calculations and Franck-Condon simulations including anharmonicity
No full textGeometrical parameters, vibrational frequencies and relative electronic energies of the X(2)B(1) state of CF(2) (-) and the X(1)A(1) and a(3)B(1) states of CF(2) have been calculated. Core-electron effects on the computed minimum-energy geometries and relative electronic energies have been investigated, and relativistic contributions to the computed relative electronic energies calculated. Potential energy functions of the X(2)B(1) state of CF(2) (-) and the X(1)A(1) and a(3)B(1) states of CF(2) have been determined, and anharmonic vibrational wavefunctions of these states calculated variationally. Franck-Condon factors including anharmonicity and Duschinsky rotation have been computed and used to simulate the a-X emission spectrum of CF(2) determined by S. Koda [Chem. Phys. Lett. 1978, 55, 353] and the 364 nm laser photodetachment spectrum of CF(2) (-) obtained by R. L. Schwartz et al. [J. Phys. Chem. A 1999, 103, 8213]. Comparison between theory and experiment shows that the theoretical approach benchmarked in the present study is able to give highly reliable positions for the CF(2)(X(1)A(1))+e?CF(2) (-)(X(2)B(1)) and CF(2)(a(3)B(1))+e?CF(2) (-)(X(2)B(1)) bands in the photoelectron spectrum of CF(2) (-) and a reliable singlet-triplet gap for CF(2). It is therefore concluded that the same theoretical approach should give reliable simulated CCl(2)(X(1)A(1))+e?CCl(2) (-)(X(2)B(1)) and CCl(2)(a(3)B(1))+e?CCl(2) (-)(X(2)B(1)) bands in the photodetachment spectrum of CCl(2) (-) and a reliable singlet-triplet gap for CCl(2)
Franck-condon simulations including anharmonicity of the a-x and SVL emission of HSiCl and DSiCl
No full textRCCSD(T) and/or CASSCF/MRCI calculations have been carried out on the 1A? and 1A?? states of HSiCl employing basis sets of up to the aug-cc-pV5Z quality. Contributions from core correlation and extrapolation to the complete basis set limit were included in determining the computed equilibrium geometrical parameters and relative electronic energy of these two states of HSiCl. Franck?Condon factors which include allowance for anharmonicity and Duschinsky rotation between these two states of HSiCl and DSiCl were calculated employing RCCSD(T) and CASSCF/MRCI potential energy functions, and were used to simulate the 1A?? ? 1A? absorption and 1A?? ? 1A? single vibronic level (SVL) emission spectra of HSiCl and DSiCl. Simulated absorption and experimental LIF spectra, and simulated and observed 1A??(0,0,0) ? 1A? SVL emission spectra, of HSiCl and DSiCl are in very good agreement. However, agreement between simulated and observed 1A??(0,1,0) ? 1A? and 1A??(0,2,1) ? 1A? SVL emission spectra of DSiCl is not as good. Preliminary calculations on low-lying excited states of HSiCl suggest that vibronic interaction between low-lying vibrational levels of the 1A?? state and highly excited vibrational levels of the 3A?? is possible. Such vibronic interaction may change the character of the low-lying vibrational levels of the 1A?? state, which would lead to perturbation in the SVL emission spectra from these vibrational levels.<br/
A combined ab initio/Franck-Condon study of the Ã-X single-vibronic-level emission spectrum of CCl<sub>2</sub> and the photodetachment spectrum of CCl
No full textState-of-the-art ab initio calculations have been carried out on the X1A1, a3B1 and A1B1 states of CCl2 and the (XB1)-B-2 state of CCl2-. Franck-Condon factors including anharmonicity have been calculated, between the CCl2 states, and between the CCl2- X2B1 state and the CCl2 states. They are used to simulate the A-X single-vibronic-level (SVL) emission spectra of CCl2 determined by MA. Lui et a]. [PCCP 2003, 5, 352] and the 364 nm laser photo detachment spectrum of CCl2- obtained by R. L. Schwartz et al. [J. Phys. Chem. A 7999, 103, 8213]. Comparison between simulated and observed spectra confirms the vibrational assignments of the X2B1 SVL emission spectra and the T0 position of the A(1)B1 state of CCl2. For the photodetachment spectrum of CCl2-, spectral simulation shows that the higher binding energy 6 3 B, (CCl2) CCl2-X2B1 detachment process. Further ab initio calculations carried out in the present investigation support the suggestion that the second band in the 364 nm photodetachment spectrum of CCl2- is due to detachment from an excited state of CCl2-, a linear quartet state, to a triplet state of CC12. These calculations identify the anionic state to be the lowest (4)Sigma(g)(-) ((4)Sigma(-)) state, which photodetaches vertically to the (3)Sigma(g)(-) ((3)Sigma(-); adiabatically a3B1 and/or (3)Pi(u) ((3)Pi) states of CCl2 to give the second band observed in the 364 nm photodetachment spectrum of CCl2-
Ab initio calculations on the (A)over-tilde(1)Pi and (X)over-tilde(1)Sigma(+) states of AlNC and simulation of the AlNC (A)over-tilde (1)Pi-(X)over-tilde(1)Sigma(+) emission spectra
No full textGeometry optimization and harmonic vibrational frequencies calculations were carried out on the (A) over tilde (1)Pi and (X) over tilde states of AlNC, employing a variety of ab initio molecular orbital methods, including the SERHF, CIS, MP2, and QCISD methods, with basis sets up to the size of the cc-pVQZ basis set. In addition, single-point energy calculations at the CCSD(T) and CASSCF/MRCI levels were performed to determine the transition energy (T,) between the two electronic states. Franck-Condon calculations were carried out for the (A) over tilde (1)Pi- (X) over tilde (1)Sigma +SVL emission, with the geometry of the ground state being fixed to the available experimental geometry. The best match between the simulated and observed spectra gave the first experimentally derived geometry of the (A) over tilde (1)Pi state (Al-N = 1.785 +/- 0.005 Angstrom and N-C = 1.150 +/- 0.008 Angstrom)
Ab initio calculations on PO2 and anharmonic Franck-Condon simulations of its single-vibrational-level emission spectra
No full textGeometry optimisation and harmonic vibrational frequency calculations were carried out on some low-lying electronic states Of PO2 at the CIS, CASSCF, MP2, and RCCSD(T) levels with various standard basis sets of at least valence triple-zeta quality. Relative electronic energies, including vertical excitation energies from the (X) over tilde (2)A(1) state {with the electronic configuration of... (7a(1))(2)(8a(1))(1)} and T-e values, were computed at the RCCSD(T) and CASSCF/MRCI levels with basis sets of up to aug-cc-pVQZ quality. These computed results, particularly the computed T, values, suggest that the upper electronic state of the laser induced fluorescence (LIF) and single-vibrational-level (SVL) emission spectra Of PO2 reported recently by Lei et al. [J. Phys. Chem. A 2001, 165, 7828] is the 2(2)A(1) state Of PO2 {with the electronic configuration of... (7a(1))(1)(8a(1))(2)}. RCCSD(T)/ aug-cc-pVQZ and CASSCF/MRCI/aug-cc-pVQZ(no g) energy scans were carried out on the (X) over tilde (2)A(1) and 2(2)A(1) states Of PO2, respectively, in the symmetric stretching and bending coordinates. Franck-Condon factors (FCFs) between the two states, which allow for the Duschinsky and anharmonic effects, were calculated employing the potential energy functions obtained from the,ab initio scans. Comparison between the simulated spectra based on the computed FCFs and observed SVL emission spectra led to reassignments of the vibrational designations of the emitting SVLs in the upper state. On the basis of the excellent agreement between the simulated spectra for the revised SVLs and the observed emission spectra, the electronic transition involved in the LIF and SVL emission spectra reported by Lei et al. is confirmed to be 2(2)A(2)-(X) over tildeA(1) of PO2. Following the revised vibrational assignments of the upper electronic state in the SVL emissions, the vibrational assignments of the LIF excitation bands given by Lei et al. are revised and a revised To value of 30660 cm(-1) is estimated for the 2(2)A(1) state of PO2. In addition, employing the iterative Franck-Condon analysis (IFCA) procedure in the simulation of the SVL emission spectra, the equilibrium geometry of the 2(2)A(1) state of PO2 is derived for the first time (r(e) = 1.560 Å; ?(e) = 116.5°)
Simulation of the single-vibronic-level emission spectrum of HPS
No full textWe have computed the potential energy surfaces of the X˜1A? and A˜1A'' states of HPS using the explicitly correlated multi-reference configuration interaction (MRCI-F12) method, and Franck–Condon factors between the two states, which include anharmonicity and Duschinsky rotation, with the aim of testing the assignment of the recently reported single-vibronic-level (SVL) emission spectrum of HPS [R. Grimminger, D. J. Clouthier, R. Tarroni, Z. Wang, and T. J. Sears, J. Chem. Phys.139, 174306 (2013)]. These are the highest level calculations on these states yet reported. It is concluded that our spectral simulation supports the assignments of the molecular carrier, the electronic states involved and the vibrational structure of the experimental laser induced fluorescence, and SVL emission spectra proposed by Grimminger et al. [J. Chem. Phys.139, 174306 (2013)]. However, there remain questions unanswered regarding the relative electronic energies of the two states and the geometry of the excited state of HPS
A combined ab initio and Franck-Condon factor simulation study on the photdetachmnent spectrumn of the HfO2 anion
No full textRestricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} potential energy functions (PEFs) of the X̃ 1A1 state of HfO2 and the X̃ 2A1 state of HfO2 - were computed, employing the quasi-relativistic effective core potential, ECP60MWB, and an associated contracted [13s6p6d4f3g2h] basis set designed for Hf, and the augmented correlation-consistent polarized valence quadruple-zeta (aug-cc-pVQZ) basis set for O. Based on the differences between the computed r0 and re geometrical parameters obtained from the PEF, and available experimentally derived r0 geometrical parameters of the X̃ 1A1 state of HfO2, the experimental r e geometrical parameters of the X̃ 1A1 state of HfO2 were estimated as:-re(HfO) = 1.7751 Å and θe(OHfO) = 107.37°. In addition, Franck-Condon factors for the HfO2 (X̃ 1A1) + e ← HfO 2 - (X̃ 2A1) electron detachment process, which include allowance for Duschinsky rotation and anharmonicity, were calculated using the computed RCCSD(T) PEFs, and were used to simulate the HfO2 (X̃ 1A1) + e← HfO 2 - (X̃ 2A1) photodetachment band of HfO2 -. Employing the estimated experimental r e geometrical parameters of the X̃ 1A1 state of HfO2 obtained in this work, the iterative Franck-Condon analysis (IFCA) procedure was carried out to optimize the geometrical parameters of the X̃ 2A1 state of HfO2 - until the simulated spectrum matched best with the experimental 355 nm photodetachment spectrum of W. Zheng, et. al., J. Phys. Chem. A, 1998, 102, 9129. The equilibrium geometrical parameters of X̃ 2A 1 state of HfO2 - derived via the IFCA procedure are re(HfO) = 1.823 Å and θe(OHfO) = 111.5°. Further calculations on low-lying triplet states of HfO2 gave adiabatic electronic energies (Te's) of, and vertical excitation energies (Tvert's) to, the ã 3B2, b̃ 3B1, c̃ 3A1 and d̃ 3A2 states of HfO2 (from the X̃ 1A1 state of HfO2), as well as electron affinities (EAs) and vertical detachment energies (VDEs) to these neutral states from the X̃ 2A1 state of HfO2 -.Department of Applied Biology and Chemical Technolog
A combined ab initio and Franck-Condon simulation study of the photodetachment spectrum of ZrO2
No full textRCCSD(T) potential energy functions (PEFs) of the state of ZrO2 and the state of have been computed employing the fully relativistic ECP28MDF ECP and associated aug-cc-pwCVQZ basis set for Zr (aug-cc-pVQZ for O). These PEFs were used in variational calculations of anharmonic vibrational wavefunctions of the ground electronic states of ZrO2 and . Franck–Condon factors which include allowance of Duschinsky rotation between these two electronic states were then computed and used to simulate the photodetactment spectrum of . Excellent agreement between the simulated and observed spectra is obtained, confirming the reliability of the PEFs used
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