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

Recent advances in the compound-oriented and pattern-oriented approaches to the quality control of herbal medicines

The current approaches to the quality control of herbal medicines are either compound-oriented or pattern-oriented, the former targeting specific components with some known chemical properties and the latter targeting all detectable components. The marker approach uses specific chemical compounds with known molecular structures, while the multi-compound approach uses both chemical compounds with known structures and those with partial chemical information e.g. retention times, mass spectra and ultraviolet spectra. Apart from chromatographic techniques, new techniques such as oscillating and electrochemistry fingerprints have been developed for quality control. Chemometric resolution methods are widely used for component deconvolution and data comparison. Pattern recognition techniques are used for authentication of herbal medicines

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Photoelectron spectroscopy of some polyatomic molecules

The photoelectron spectrum of a molecule displays the kinetic energy distribution of the ejected photoelectron by monochromatic radiation. From the fine structure on a photoelectron band, valuable information about the bonding properties of both the molecule and its cation, and the ionic geometry can be obtained. The work described in this thesis falls into two main parts. The first is concerned with the quantitative application of the Franck-Condon principle to group VI hydrides, nitrous oxide and dihaloethylenes, by which the geometries of their molecular ions were obtained. An iterative method was devised to facilitate the computational procedure. The second part of this thesis contains the results of photoelectron spectroscopic studies on several halogenated molecules, viz. fluorotribromo-methane, fluorotrichloromethane, 1,2-dichloro-, 1,2 dibromo-, and 1,2 diiodo-ethanes and their perfluoro derivatives, 1,2 bromochloroethane, 1,2-dibromo-1,1-difluoroethane, cis and trans 1,2 difluoroethylenes, and 1,2 dibromo-cyclohexane. One electron models including spin orbital coupling, and through bond and through space interactions, are applied to most of these molecules as well as the dichloro-, dibromo-, and diiodoethylenes. The NMR chemical shifts, nuclear quadrupole coupling constants, electronegativity of the halogen atom and the force constants of the molecules studied are discussed in the light of the calculated molecular orbital parameters.Science, Faculty ofChemistry, Department ofGraduat

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

A new method of calculation of Franck-Condon factors which includes allowance for anharmonicity and the Duschinsky effect: Simulation of the HeI photoelectron spectrum of ClO2

A new method of Franck-Condon (FC) factor calculation for nonlinear polyatomics, which includes anharmonicity and Duschinsky rotation, is reported. Watson's Hamiltonian is employed in this method with multidimensional ab initio potential energy functions. The anharmonic vibrational wave functions are expressed as linear combinations of the products of harmonic oscillator functions. The Duschinsky effect, which arises from the rotation of the normal modes of the two electronic states involved in the electronic transition, is formulated in Cartesian coordinates, as was done previously in an earlier harmonic FC model. This new anharmonic FC method was applied to the simulation of the bands in the He I photoelectron (PE) spectrum of ClO2. For the first band, the harmonic FC model was shown to be inadequate but the anharmonic FC simulation gave a much-improved agreement with the observed spectrum. The experimentally derived geometry of the (X) over tilde (1)A(1) state of ClO2+ was obtained, for the first time, via the iterative FC analysis procedure {R(Cl-O)=1.414 +/- 0.002 Angstrom, angle O-Cl-O=121.8 +/- 0.1 degrees}. The heavily overlapped second PE band of ClO2, corresponding to ionization to five cationic states, was simulated using the anharmonic FC code. The main vibrational features observed in the experimental spectrum were adequately accounted for in the simulated spectrum. The spectral simulation reported here supports one of the two sets of published assignments for this band, which was based on multireference configuration interaction (MRCI) calculations. In addition, with the aid of the simulated envelopes, a set of adiabatic (and vertical) ionization energies to all five cationic states involved in this PE band, more reliable than previously reported, has been derived. This led also to a reanalysis of the photoabsorption spectrum of ClO2

Franck-Condon simulation of the single-vibronic-level emission spectra of HPCI/DPCl and the chemiluminescence spectrum of HPCI, including anharmonicity

Restricted-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)]

An ab initio study on the ground and low-lying doublet electronic states of SbO2

Geometry optimization and harmonic vibrational frequency calculations have been carried out on the low-lying doublet electronic states of antimony dioxide (SbO2) employing a variety of ab initio methods, including the complete active space self-consistent field/multireference configuration interaction and the RCCSD(T) methods. Both large and small core relativistic effective core potentials were used for Sb in these calculations, together with valence basis sets of up to aug-cc-pV5Z quality. Contributions from outer core correlation and off-diagonal spin-orbit interaction to relative electronic energies have been calculated. The ground electronic state of SbO2 is determined to be the X (2)A(1) state, as is the case for dioxides of other lighter group 15 p-block (or group VA) elements. However, the A B-2(2) and B (2)A(2) states are estimated to be only 4.1 and 10.7 kcal/mole above the X (2)A(1) state, respectively, at the complete basis set limit. Reliable vertical excitation energies from the X (2)A(1) state to low-lying excited states of SbO2 have been computed with a view to assist future spectral assignments of the absorption and/or laser-induced fluorescence spectra of SbO2, when they become available

Identification of essential components of Houttuynia cordata by gas chromatography/mass spectrometry and the integrated chemometric approach

Starting with Biller–Biemann's work [J.E. Biller, K. Biemann, Anal. Lett. 7 (1974) 515], various kinds of approaches have been proposed to extract GC/MS data to obtain pure components responses. In this paper, an integrated chemometric approach is proposed, which combine four sequential steps, data pretreatment, component perception, resolution and component identification, and then the proposed approach is manipulated to analyze the essential oils of a herbal medicine named Houttuynia cordata (HC). On the basis of the selective information obtained from both chromatograms and mass spectra, the proposed integrated chemometric approach can resolve the two-way GC/MS responses matrix into pure chromatograms and mass spectra without any model assumption on the peak shape. The resolution results obtained from HC samples demonstrate the performance of the proposed approach and indicate that it may be a promising one for analyzing complex chromatograms.Department of Applied Biology and Chemical Technolog