Emission spectroscopy of mixed photodissociated mercury halides

Whitehurst, Colin; King, Terence A.

doi:10.1088/0022-3727/20/12/005

Cited by 10 publications

(4 citation statements)

References 12 publications

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“…Mercuric halides, HgX 2 (X ¼ Cl, Br and I), and their photodissociation dynamics have been of much interest due to their optical and electronic properties [106][107][108][109][110][111][112][113][114][115][116][117][118][119]. They are a good model system for studying ultrafast photochemistry thanks to their simple triatomic molecular structure, high photochemical reactivity, fast recombination rates and the presence of heavy atoms [120].…”

Section: Reaction Pathways Of Hgbr 2 and Hgimentioning

confidence: 99%

Ultrafast X-ray scattering: structural dynamics from diatomic to protein molecules

Ihee

Wulff

Kim

et al. 2010

International Reviews in Physical Chemistry

104

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Recent years have witnessed the birth of picosecond pump-probe X-ray diffraction and scattering techniques, thanks to the technological developments in the third generation synchrotron beamlines and advances in theory and data analysis by combining quantum calculations, molecular dynamics simulations and global fitting analysis. Our laboratories have employed this technique to study structural dynamics and spatiotemporal kinetics of many molecular systems in solution including diatomic molecules, haloalkanes, organometallic complexes and protein molecules over timescales from picoseconds (ps) to milliseconds. The visualising power and unbiased sensitivity of X-ray scattering proved to be instrumental in identifying global reaction pathways and in some cases capturing detailed threedimensional structures of reaction intermediates. Many results have accumulated from which we have selected some interesting examples to be reviewed here. The structural dynamics of Br 2 and I 2 are compared and the reaction pathways for HgBr 2 and HgI 2 are compared. Solvents may affect the reaction pathways as illustrated in the photolysis of CH 2 I 2 in two different solvents. How does the excitation wavelength affect the reaction pathways is another important aspect in photochemistry as shown for Ru 3 (CO) 12 . Applications to the folding of cytochrome-c and the structural dynamics of myoglobin and bacteriorhodopsin are also reviewed. The time resolution is currently limited to about 100 ps, the Xray pulse width available from synchrotron sources. In the near future, X-ray free electron lasers (XFELs) will deliver 100 fs or shorter X-ray pulses. In femtosecond (fs) X-ray scattering experiments with this higher resolution, real-time observation of ultrafast chemical events, such as bond-breaking and bond-making will be possible. So far, gas-phase reactions, which are the main targets for ultrafast electron diffraction due to the high scattering power of electrons, have not yet been studied with time-resolved X-ray scattering, but in principle this discipline will become feasible with the coming XFEL sources. We thus discuss potential fs X-ray scattering experiments for gas phase as well as solution phase reactions. In addition, the high photon flux and the coherence of XFEL-generated X-ray pulses might open up new research areas, such as single-molecule diffraction.

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Section: Reaction Pathways Of Hgbr 2 and Hgimentioning

confidence: 99%

Ultrafast X-ray scattering: structural dynamics from diatomic to protein molecules

Ihee

Wulff

Kim

et al. 2010

International Reviews in Physical Chemistry

104

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“…Over the last century, mercuric halides, HgX 2 (X = Cl, Br and I), and their photodissociation dynamics have attracted much interest due to their optical and electronic properties. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Their simple triatomic molecular structure, high photochemical reactivity, fast recombination rates, and the presence of heavy atoms have made them a good model system for studying ultrafast photochemistry. 15 Accordingly, the photodissociation of HgX 2 in the gas phase has been the subject of many spectroscopic and theoretical studies.…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of HgBr2 in methanol investigated using time-resolved X-ray liquidography

Jun

Lee

Kim

et al. 2010

Phys. Chem. Chem. Phys.

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We investigate the photoinduced dissociation of HgBr(2) in methanol and the ensuring structural dynamics of the photo-products over a time span from 100 ps to 1 μs after photolysis at 267 nm by using time-resolved X-ray liquidography (TRXL). By making use of the atomic-level structural sensitivity of X-ray scattering and the superb 100 ps time resolution of X-ray pulses from a 3rd-generation synchrotron, the structural dynamics of a chemical reaction in solution can be directly monitored. The measured time-dependent X-ray solution scattering signals, analyzed using global-fitting based on DFT calculations and MD simulations, show that photoexcited HgBr(2) dissociates via both two-body (HgBr + Br) and three-body (Hg + Br + Br) dissociation pathways with a ∼2 : 1 branching ratio. Following dissociation, the photoproducts recombine via three reactions involving Br species: (1) Hg + Br, (2) HgBr + Br, and (3) Br + Br. The associated rate constants and branching ratios are determined from the global-fitting analysis. Also, we examine the energy dissipation from reacting solute molecules and relaxation of excited molecules to solvent bath accompanying the temperature rise of 0.54 K. Compared to a previous TRXL study of the photodissociation of HgI(2), the results of this work suggest that the photodissociation pathway of HgBr(2) is different from that of HgI(2), which dissociates predominantly via two-body dissociation, at least to within the currently available time resolution of ∼100 ps. In addition, the error analysis of the fit parameters used in the global-fitting are discussed in detail with a comparison of various error estimation algorithms.

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“…Before the observation of MDEs, the primary interest in gaseous mercury halides was in connection with laser applications. The UV absorption − and dissociation − of HgX 2 and the B 2 Σ + → X 2 Σ + transitions of HgX (X = Br, Cl, I) − have received a fair amount of attention. The infrared and Raman spectra of matrix-isolated − and gas-phase − HgIX (X = Br, Cl, I) have also been characterized.…”

Section: Introductionmentioning

confidence: 99%

Ab Initio Thermochemistry Involving Heavy Atoms: An Investigation of the Reactions Hg + IX (X = I, Br, Cl, O)

2005

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Accurate 0 K enthalpies have been calculated for reactions of mercury with a series of small iodine-containing molecules (I2, IBr, ICl, and IO). The calculations have been carried out with the coupled cluster singles and doubles method with a perturbative correction for connected triple excitations [CCSD(T)] using sequences of correlation consistent basis sets and accurate relativistic pseudopotentials. Corrections have been included to account for core-valence correlation, spin-orbit coupling, scalar relativity, and the Lamb shift. In a few cases coupled cluster calculations with iterative triple (CCSDT) and quadruple (CCSDTQ) excitations have been carried out to estimate the effects of higher order electron correlation. The pseudopotential calculations have also been compared to all electron calculations using second- and third-order Douglas-Kroll-Hess Hamiltonians. In addition to the reaction enthalpies, heats of formation, bond lengths, and harmonic vibrational frequencies have been calculated for the stable triatomic products HgI2, HgIBr, HgICl, and HgIO. Accurate dissociation energies, equilibrium bond lengths, and harmonic vibrational frequencies have also been calculated for each of the diatomic molecules involved in this study (HgI, HgBr, HgCl, HgO, I2, IBr, ICl, and IO). The reported enthalpies are expected to have accuracies of 1 kcal/mol or better.

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Emission spectroscopy of mixed photodissociated mercury halides

Cited by 10 publications

References 12 publications

Ultrafast X-ray scattering: structural dynamics from diatomic to protein molecules

Ultrafast X-ray scattering: structural dynamics from diatomic to protein molecules

Photochemistry of HgBr2 in methanol investigated using time-resolved X-ray liquidography

Ab Initio Thermochemistry Involving Heavy Atoms: An Investigation of the Reactions Hg + IX (X = I, Br, Cl, O)

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