Galina Kerenskaya

University of California, Irvine, Irvine, California, United States

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Publications (15)44.57 Total impact

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    ABSTRACT: Immediately on the discovery of the halogen molecules, their chemistry was closely linked with that of water. For some time, it was thought that water was a constituent of chlorine. The brightly coloured halogens have played an important role in spectroscopy almost from the beginning of its use as a quantitative tool for understanding molecular structure. Already in the 19th century, the remarkable colour change upon dissolving iodine in aqueous solution was noted and studied. However, a complete, microscopic explanation for this phenomenon is yet to be achieved. We review this field and propose that the time is right to achieve this fundamental goal of chemical physics for the halogen-water system. In addition, we review recent work on the UV-vis, Raman and ultrafast dynamics studies of halogen molecules in clathrate hydrate cages, spectroscopy of water-halogen dimer molecules and theory of small water-halogen clusters. Based on recent findings, we propose a variety of `next steps' for the complete understanding of this fascinating model system.
    International Reviews in Physical Chemistry 01/2009; 28(2):223-265. DOI:10.1080/01442350903017302 · 4.92 Impact Factor
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    ABSTRACT: We report transient grating measurements carried out on single crystals of bromine clathrate hydrates and on bromine dissolved in water. In all cases, excitation into the B-state of Br2 leads to prompt predissociation, followed by cage-induced recombination on the A/A' electronic surfaces. In liquid water, the vibrationally incoherent recombinant population peaks at t=1 ps and decays with a time constant of 1.8 ps. In the hydrate crystals, the recombination is sufficiently impulsive to manifest coherent oscillations of the reformed bond. In tetragonal TS-I crystals, with the smaller cages, the recombination is fast, t=360 fs, and the bond oscillation period is 240 fs. In cubic CS-II crystals, the recombination is slower, t=490 fs, and the visibility of the vibrational coherence, which shows a period of 290 fs, is significantly reduced due to the larger cages and the looser fit around bromine. The mechanical cage effect is quantified in terms of the recombination time-distribution, the first three moments of which are associated with size, structural rigidity, and anelasticity of the cage. In the crystalline cages, the distribution is symmetric about the mean: mean time tm=300 fs, 400 fs and standard deviation sigma=70 fs, 100 fs, in TS-I and CS-II, respectively. The finding is consistent with the assignment of occupied cages: principally 5(12)6(2) polyhedra in TS-I and 5(12)6(4) polyhedra in CS-II. In liquid water, with diffuse cages, the distribution characterized by tm=555 fs and sigma=400 fs, is strongly skewed (gamma1=1.88) toward delayed recombination-the effective liquid phase hydration shell is larger than that in a hydrate phase, structurally disordered, and anelastic. Information about dipolar disorder, comparable in all three media, is extracted from electronic predissociation rates of the B-state, which is sensitive to the symmetry in the guest-host interaction.
    Physical Chemistry Chemical Physics 01/2009; 10(48):7226-32. DOI:10.1039/b811529j · 4.20 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 04/2008; 39(16). DOI:10.1002/chin.200816008
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    ABSTRACT: The structure and composition of bromine clathrate hydrate has been controversial for more than 170 years due to the large variation of its observed stoichiometries. Several different crystal structures were proposed before 1997 when Udachin et al. (Udachin, K. A.; Enright, G. D.; Ratcliffe, C. I.; Ripmeester, J. A. J. Am. Chem. Soc. 1997, 119, 11481) concluded that Br2 forms only the tetragonal structure (TS-I). We show polymorphism in Br2 clathrate hydrates by identifying two distinct crystal structures through optical microscopy and resonant Raman spectroscopy on single crystals. After growing TS-I crystals from a liquid bromine-water solution, upon dropping the temperature slightly below -7 degrees C, new crystals of cubic morphology form. The new crystals, which have a limited thermal stability range, are assigned to the CS-II structure. The two structures are clearly distinguished by the resonant Raman spectra of the enclathrated Br2, which show long overtone progressions and allow the extraction of accurate vibrational parameters: omega(e) = 321.2 +/- 0.1 cm(-1) and omega(e)x(e) = 0.82 +/- 0.05 cm(-1) in TS-I and omega(e) = 317.5 +/- 0.1 cm(-1) and omega(e)x(e) = 0.70 +/- 0.1 cm(-1) in CS-II. On the basis of structural analysis, the discovery of the CS-II crystals implies stability of a large class of bromine hydrate structures and, therefore, polymorphism.
    The Journal of Physical Chemistry A 03/2008; 112(5):787-9. DOI:10.1021/jp077562q · 2.78 Impact Factor
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    ABSTRACT: UV-vis and Raman spectroscopy were used to study iodine molecules trapped in sII clathrate hydrate structures stabilized by THF, CH(2)Cl(2), or CHCl(3). The spectra show that the environment for iodine inside the water cage is significantly less perturbed than either in aqueous solution or in amorphous water-ice. The resonance Raman progression of I(2) in THF clathrate hydrate can be observed up to v = 6 when excited at 532 nm. The extracted vibrational frequency omega e = 214 +/- 1 cm(-1) is the same as that of the free molecule to within experimental error. At the same time, the UV-vis absorption spectrum of I(2) in the sII hydrate exhibits a relatively large, 1440 cm(-1), blue-shift. This is mainly ascribed to the differential solvation of the I(2) electronic states. We conclude that iodine in sII hydrate resides in a 5(12)6(4) cavity, in which the ground-state I(2) potential is not significantly perturbed by the hydrate lattice. In contrast, in water and in ice, the valence absorption band of I(2) is dramatically broadened and blue-shifted by 3000 cm(-1), and the resonance Raman scattering is effectively quenched. These observations are shown to be consistent with a strong interaction between water molecule and iodine through the lone pair of electrons on water as in the case of bromine in the same media. The results presented here, and the stability of other halogen hydrates, were used to test the predictions of simple models and force-field calculations of the host cage-guest association energy.
    The Journal of Physical Chemistry A 12/2007; 111(43):10969-76. DOI:10.1021/jp0747306 · 2.78 Impact Factor
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    ABSTRACT: We report the first UV-vis spectroscopic study of bromine molecules confined in clathrate hydrate cages. Bromine in its natural hydrate occupies 51262 and 51263 lattice cavities. Bromine also can be encapsulated into the larger 51264 cages of a type II hydrate formed mainly from tetrahydrofuran or dichloromethane and water. The visible spectra of the enclathrated halogen molecule retain the spectral envelope of the gas-phase spectra while shifting to the blue. In contrast, spectra of bromine in liquid water or amorphous ice are broadened and significantly more blue-shifted. The absorption bands shift by about 360 cm-1 for bromine in large 51264 cages of type II clathrate, by about 900 cm-1 for bromine in a combination of 51262 and 51263 cages of pure bromine hydrate, and by more than 1700 cm-1 for bromine in liquid water or amorphous ice. The dramatic shift and broadening in water and ice is due to the strong interaction of the water lone-pair orbitals with the halogen sigma* orbital. In the clathrate hydrates, the oxygen lone-pair orbitals are all involved in the hydrogen-bonded water lattice and are thus unavailable to interact with the halogen guest molecule. The blue shifts observed in the clathrate hydrate cages are related to the spatial constraints on the halogen excited states by the cage walls.
    The Journal of Physical Chemistry A 01/2007; 110(51):13792-8. DOI:10.1021/jp064523q · 2.78 Impact Factor
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    ABSTRACT: The A2delta-X2pi transition of CH-Ne was examined using laser-induced fluorescence and fluorescence depletion techniques. The spectrum was found to be particularly congested due to the large number of bound states derived from the CH(A,n=2)+Ne interaction, and the small energy spacings between these states resulting from the relatively weak anisotropy of the van der Waals bond. High-level ab initio calculations were used to generate two-dimensional potential energy surfaces for CH(X)-Ne and CH(A)-Ne. The equilibrium structures from these surfaces were bent and linear for the X and A states, respectively. Variational calculations were used to predict the bound states supported by the ab initio surfaces. Empirical modification of the potential energy surfaces for the A state was used to obtain energy-level predictions that were in good agreement with the experimental results. Transitions to all of the optically accessible internal rotor states of CH(A,n=2)-Ne were identified, indicating that CH performs hindered internal rotations in the lowest-energy levels of the A and X states. The characteristics of the potential energy surfaces for CH-Ne in the X,A,B, and C states suggest that dispersion and exchange repulsion forces dominate the van der Waals interaction.
    The Journal of Chemical Physics 09/2005; 123(5):054304. DOI:10.1063/1.1946747 · 3.12 Impact Factor
  • Wafaa M Fawzy, Galina Kerenskaya, Michael C Heaven
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    ABSTRACT: The H2-NH(X) van der Waals complex has been examined using ab initio theory and detected via fluorescence excitation spectroscopy of the A(3)Pi-X(3)Sigma(-) transition. Electronic structure calculations show that the minimum energy geometry corresponds to collinear H2-NH(X), with a well depth of D(e)=116 cm(-1). The potential-energy surface supports a secondary minimum for a T-shaped geometry, where the H atom of NH points towards the middle of the H2 bond (C(2v) point group). For this geometry the well depth is 73 cm(-1). The laser excitation spectra for the complex show transitions to the H2+NH(A) dissociative continuum. The onset of the continuum establishes a binding energy of D(0)=32+/-2 cm(-1) for H2-NH(X). The fluorescence from bound levels of H2-NH(A) was not detected, most probably due to the rapid reactive decay [H2-NH(A)-->H+NH2]. The complex appears to be a promising candidate for studies of the photoinitiated H2+NH abstraction reaction under conditions were the reactants are prealigned by the van der Waals forces.
    The Journal of Chemical Physics 04/2005; 122(14):144318. DOI:10.1063/1.1879932 · 3.12 Impact Factor
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    ABSTRACT: A study of NH/D-Ne was undertaken to investigate the structure of this complex and examine the ability of high-level theoretical methods to predict its properties. The A 3pi-X 3sigma- transition was characterized using laser induced fluorescence measurements. Results from theoretical calculations were used to guide the interpretation of the spectra. Two-dimensional potential energy surfaces were calculated using second-order multireference perturbation theory with large correlation consistent basis sets. The potential energy surfaces were used to predict the ro-vibronic structure of the A-X system. Calculated ro-vibronic energy level patterns could be recognized in the spectra but quantitative discrepancies were found. These discrepancies are attributed to incomplete recovery of the dynamical correlation energy.
    Physical Chemistry Chemical Physics 03/2005; 7(5):846-54. · 4.20 Impact Factor
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    ABSTRACT: A study of NH/D–Ne was undertaken to investigate the structure of this complex and examine the ability of high-level theoretical methods to predict its properties. The A 3Π–X 3Σ− transition was characterized using laser induced fluorescence measurements. Results from theoretical calculations were used to guide the interpretation of the spectra. Two-dimensional potential energy surfaces were calculated using second-order multireference perturbation theory with large correlation consistent basis sets. The potential energy surfaces were used to predict the ro-vibronic structure of the A–X system. Calculated ro-vibronic energy level patterns could be recognized in the spectra but quantitative discrepancies were found. These discrepancies are attributed to incomplete recovery of the dynamical correlation energy.
    Physical Chemistry Chemical Physics 01/2005; 7. DOI:10.1039/b415253k · 4.20 Impact Factor
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    ABSTRACT: The NH-He van der Waals complex was characterized via laser excitation of bands associated with the NH A (3)Pi-X (3)Sigma(-) transition. It was demonstrated that the ground state supports a bound level with a rotational constant of B'=0.334(2) cm-1. These results are in agreement with the predictions of recent high-level theoretical calculations. Spin-orbit predissociation of the excited complex was observed, and the spectra yield insights regarding the NH(A)+He potential energy surfaces. (C) 2004 American Institute of Physics.
    The Journal of Chemical Physics 11/2004; 121(16):7549-52. DOI:10.1063/1.1808416 · 3.12 Impact Factor
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    Galina Kerenskaya, Udo Schnupf, Michael C. Heaven
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    ABSTRACT: A study of NH/D–Ne was undertaken to investigate the structure of this complex and examine the ability of high-level theoretical methods to predict its properties. The c 1Π–a 1Δ transition was characterized using laser induced fluorescence measurements. Spectra recorded in the vicinity of the monomer show groups of complex features associated with the monomer P(2), Q(2), and R(2) lines. The present study focused on the low-energy bands associated with P(2). Results from theoretical calculations were used to guide the interpretation of the spectra. Two-dimensional potential energy surfaces were calculated using second-order multireference perturbation theory with large correlation consistent basis sets. The potential surfaces were used to predict the rovibronic structure of the c–a system. Calculated rovibronic energy level patterns could be recognized in the spectra but quantitative discrepancies were found. For the a and c states the ab initio potentials were found to be too shallow, and for the c state the equilibrium intermolecular separation was too short. These errors are attributed to incomplete recovery of the dynamical correlation energy.
    The Journal of Chemical Physics 10/2003; 119(16). DOI:10.1063/1.1611876 · 3.12 Impact Factor
  • Galina Kerenskaya, Alexey L. Kaledin, Michael C. Heaven
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    ABSTRACT: Two-dimensional intermolecular potential energy surfaces for the CH(A 2Δ)–Ar complex (CH bond fixed at equilibrium) have been calculated at the multireference singles and doubles configuration interaction/correlation-consistent valence quadruple zeta level of theory. These surfaces are of 2 2A′ and 2 2A″ electronic symmetry. Both potentials define a linear CH–Ar equilibrium structure (Ar…H∼3 Å), with a secondary minimum for the Ar–CH linear geometry (Ar…C∼4 Å). The global minimum is ∼117 cm−1 below dissociation. Side-on approach of the Ar atom breaks the orbital degeneracy of the 2Δ state, but this splitting is relatively small near the equilibrium separation, only about 10 cm−1. The potential surfaces have been used in simulations of the A–X bands of CH/D–Ar. The correlation between the simulated and observed spectra was sufficient for assignment of the latter. Systematic adjustment of the A state average potential, defined as Va = (VA′+VA″)/2, was made to obtain a surface that reproduces the vibrational energy spacings and rotational constants of CH/D–Ar. © 2001 American Institute of Physics.
    The Journal of Chemical Physics 07/2001; 115(5):2123-2133. DOI:10.1063/1.1382647 · 3.12 Impact Factor
  • Amy Burroughs, Galina Kerenskaya, Michael C. Heaven
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    ABSTRACT: The I2–Ne complex has been examined using double resonance and fluorescence depletion techniques. Action spectra for I2(B,v)–Ne, detected by monitoring the I2(B,v−1) predissociation fragments, show that the Δν = −1 predissociation channel is less efficient for levels above v = 32 (with no excitation of the intermolecular vibrations), and closed for v>36. From these data we obtained a revised estimate for the dissociation energy for I2(B)–Ne of D0 = 57.6±1.0 cm−1. Action spectra for I2(B,v = 34)–Ne, detected by monitoring I2(B,v = 33) fragments, revealed a progression of intermolecular vibrational levels that had not been observed previously. These levels have been assigned to T-shaped, linear, and delocalized states of I2(B,v = 34)–Ne. Assignments were based on characteristic vibrational distributions exhibited by the I2(B,v−Δv) predissociation fragments. Fluorescence depletion measurements show that all of the bands in the action spectrum originate from a common ground state level. Furthermore, the one atom cage effect fluorescence from I2(B)–Ne can be depleted by transitions from the zero-point level of I2(X)–Ne. These observations indicate that the ground state wave function is delocalized, sampling both the T-shaped and linear configurations of the complex. © 2001 American Institute of Physics.
    The Journal of Chemical Physics 07/2001; 115(2):784-791. DOI:10.1063/1.1378317 · 3.12 Impact Factor