Simulation of the photodetachment spectrum of HHfO- using coupled-cluster calculations

The photodetachment spectrum of HHfO? was simulated using restricted-spin coupled-cluster single-double plus perturbative triple {RCCSD(T)} calculations performed on the ground electronic states of HHfO and HHfO?, employing basis sets of up to quintuple-zeta quality. The computed RCCSD(T) electron affinity of 1.67 ± 0.02 eV at the complete basis set limit, including Hf 5s25p6 core correlation and zero-point energy corrections, agrees well with the experimental value of 1.70 ± 0.05 eV from a recent photodetachment study [X. Li et al., J. Chem. Phys. 136, 154306 (2012)]. For the simulation, Franck-Condon factors were computed which included allowances for anharmonicity and Duschinsky rotation. Comparisons between simulated and experimental spectra confirm the assignments of the molecular carrier and electronic states involved but suggest that the experimental vibrational structure has suffered from poor signal-to-noise ratio. An alternative assignment of the vibrational structure to that suggested in the experimental work is presented

Ab initio calculations on SF2 and its low-lying cationic states: Anharmonic Franck-Condon simulation of the uv photoelectron spectrum of SF2

Geometry 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

Ab initio calculations on low-lying electronic states of TeO2 and Franck-Condon simulation of the (1)¹B2?X¹ TeO2 absorption spectrum including anharmonicity

Ab initio calculations have been carried out on low-lying singlet and triplet states of TeO2 at different levels of theory with basis sets of up to the augmented-polarized valence-quintuple-zeta quality. Equilibrium geometrical parameters, harmonic vibrational frequencies, and relative electronic energies of the (X) over tilde (1)A(1), B-1(1), B-1(2), (1)A(2), (3)A(1), B-3(1), B-3(2), and (3)A(2) states of TeO2 have been calculated. Potential energy functions (PEFs) of the (X) over tilde (1)A(1) and the (1)B-1(2) states were computed at the complete-active-space self-consistent-field multireference configuration interaction level, with a basis set of augmented-polarized valence-quadruple-zeta quality. Franck-Condon factors (FCFs) for the electronic transition between the (X) over tilde (1)A(1) and (1)B-1(2) states of TeO2 were calculated with the above-mentioned ab initio PEFs. The (1)B-1(2)<--(X) over tilde (1)A(1) absorption spectrum of TeO2 was simulated employing the computed FCFs, which include Duschinsky rotation and anharmonicity, and compared with the recently published laser-induced fluorescence (LIF) spectrum of Hullah and Brown [J. Mol. Spectrosc. 200, 261 (2000)]. The ab initio results and spectral simulation reported here confirm the upper electronic state involved in the LIF spectrum to be the (1)B-1(2) state of TeO2 and also confirm the vibrational assignments of Hullah and Brown. However, our simulated spectrum suggests that the reported LIF spectrum from 345 to 406 nm represents only a portion of the full (1)B-1(2)<--(X) over tilde (1)A(1) absorption spectrum of TeO2, which extends from ca. 406 to 300 nm. Another dye other than the two used by Hullah and Brown is required to cover the 345-300 nm region of the LIF band. Ab initio calculations show strong configuration mixing of the (1)B-1(2) electronic surface with higher B-1(2) states in a region of large TeO bond length (greater than or equal to2.0 Angstrom) and OTeO bond angle (greater than or equal to135.0degrees)

Franck-Condon simulation of the single vibronic level emission spectra of HSiF and DSiF including anharmonicity

Potential energy functions (PEFs) of the (X) over tilde (1)A' and (A) over tilde (1)A" states of HSiF have been computed using the coupled-cluster single-double plus perturbative triple excitations and complete-active-space self-consistent-field multireference internally contracted configuration interaction methods, respectively, employing augmented correlation-consistent polarized-valence quadruple-zeta basis sets. For both electronic states of HSiF and DSiF, anharmonic vibrational wavefunctions and energies of all three modes have been calculated variationally with the ab initio PEFs and using Watson's Hamiltonian for nonlinear molecules. Franck-Condon factors between the two electronic states, allowing for Duschinsky rotation, were computed using the calculated anharmonic vibrational wavefunctions. These Franck-Condon factors were used to simulate the single vibronic level (SVL) emission spectra recently reported by Hostutler in J. Chem. Phys. 114, 10728 (2001). Excellent agreement between the simulated and observed spectra was obtained for the (A) over tilde (1)A"(1,0,0)-->(X) over tilde (1)A' SVL emission of HSiF. Discrepancies between the simulated and observed spectra of the (A) over tilde (1)A"(0,1,0) and (1,1,0) SVL emissions of HSiF have been found. These are most likely, partly due to experimental deficiencies and, partly to inadequacies in the ab initio levels of theory employed in the calculation of the PEFs. Based on the computed Franck-Condon factors, minor revisions of previous vibrational assignments are suggested. The calculated anharmonic wave functions of higher vibrational levels of the (X) over tilde (1)A' state show strong mixings between the three vibrational modes of HSi stretching, bending, and SiF stretching

Accurate potential energy curves for HeO-, NeO-, and ArO-: spectroscopy and transport coefficients

We calculate accurate potential energy curves for HeO-, NeO-, and ArO-, including the full counterpoise correction and allowing for spin-orbit effects. Comparison with previous curves is presented, where these are available. The three curves, (2)Sigma(1/2)(+) and (2)Pi(1/2), (2)Pi(3/2) are used to derive spectroscopic constants and to calculate the transport coefficients. for O- moving in a bath of the respective rare gas. Conclusions are made based on a comparison with the available data

Interaction potential and transport properties of NeO+

The results of both experimental and theoretical studies of the mobility of O+ in Ne are reported. Errors in the experiments have been carefully assessed, allowing the obtained data to serve as stringent tests of the ab initio potentials. These potentials were calculated using the RCCSD(T) method, employing basis sets of quintuple-zeta quality. Curves were calculated for the lowest 4Sigma? state [arising from O+(4S) interacting with Ne] and for the 2Pi state [arising from O+(2D) interacting with Ne]. Then, the effects of spin-orbit coupling were incorporated by using the Breit-Pauli operator. The resulting ground state (Omega=3/2) of NeO+ gives mobility values in good agreement with experiment at all field strengths. Values of spectroscopic quantities for the ground electronic state of NeO+ are also presented

Preliminary calculations on the Na-N-2 complex

High-level, RCCSD(T), calculations are performed on the molecular complex formed between a Na(S-2) atom and a N-2(X(1)Sigma(g)(+)) 9 molecule, using large basis sets. The complex is found to have a linear global minimum, with a D, value of only 24 cm(-1). The zeropoint energy is estimated to be around 16 cm(-1), suggesting that this is a very floppy complex. In addition, a T-shaped saddle-point lies only 7.5 cm(-1) above the potential energy minimum

Structure and thermodynamics of KO3 and KO3+

The KO3 and KO3+ species are both calculated to have C-2v diamond structures, with a trans planar geometry lying higher in energy. For the cation, the energy difference between these two structures is only similar to1 ~ mol(-1). We calculate binding energies of the two species and obtain values of 126 +/- 1 and 8 +/- 1 kcal mol(-1), for K+...03 and K+...O3, respectively. The adiabatic ionization energy is determined as 7.0 +/- 1 eV and DeltaH(f)(0 K) values of -17 +/- 2 and 149 +/- 2 kcal mol(-1) are obtained for KO3 and KO3+ respectively.

Structures and vibrational frequencies of NaO₃ and NaO₃⁺: the ionization energy of NaO₃

We use high-level ab initio, up to RCCSD(T), and the density functional theory (DFT) method, B3LYP, to obtain the geometry, vibrational frequencies, and heats of formation of NaO3(X~2B1) and NaO3+(X~1A1). In both cases, a C-2v, diamond structure is deduced. These values allow us also to derive the adiabatic ionization energy. We obtain the following values: ΔHf[NaO3,0K] = -13 ± 2 kcal mol-1, ΔHf[NaO3+,0K] = 167 ± 2 kcal mol-1, and AIE(NaO3) = 7.80 ± 0.05 eV. In addition, it was found that the B3LYP functional performs very well for the O3- species: both geometry and vibrational frequencies. For O3, the method performed well for the geometry, but not so well for the vibrational frequencies. Comparison is made where appropriate to experimental data and to previous calculations. Finally, ΔHr is calculated for a range of reactions that may contribute to the formation of NaO3 or NaO3+ in the atmosphere

Ionization energy of KOH and the dissociation energies of KOH and KOH+

High level ab initio, up to RCCSD(T), and B3LYP calculations were employed to calculate thermochemical properties for KOH and KOH+. Basis sets were of both all-electron and effective core potential (ECP) types: in both cases large, flexible valence basis sets were used, and the largest basis sets were of quintuple-zeta quality. Both KOH and KOH+ were found to be linear; in the latter case, the Renner-Teller effect is discussed. The results are close to convergence with regard to both basis sets and levels of theory. The most reliable quantities are: first AIE(KOH)=7.38+/-0.02 eV; D-0(K...OH)=82+/-1 kcal mol(-1); D-0(K+...OH)=11.4+/-1 kcal mol(-1); DeltaH(f)(KOH, 298 K) = -53+/-1 kcal mol(-1); and DeltaH(f)(KOH+, 298 K)=119+/-1 kcal mol(-1)