Novel Resonance Raman Enhancement of Local Structure around Solvated Electrons in Water

Mizuno, Misao; Tahara, Tahei

doi:10.1021/jp0119173

Cited by 41 publications

(65 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…35 First, they assumed that the GSB component was the same as the equilibrium absorption spectrum and did not change with time. This assumption has been tested by multiple TA, 56,59 photon echo, 38,60 and resonance Raman [61][62][63] experiments, all of which verify that the ground-state absorption of the hydrated electron is homogeneously broadened so there indeed should be no spectral diffusion in the GSB. Second, Barbara and co-workers assumed that the spectrum of the HGS electron was the same as that of an equilibrium hydrated electron but at a higher effective temperature and that this effective temperature relaxed exponentially with time.…”

Section: A Modeling the Hydrated Electron's Lifetime With Transient mentioning

confidence: 95%

Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

Farr

Zho

Challa

et al. 2017

The Journal of Chemical Physics

View full text Add to dashboard Cite

The structure of the hydrated electron, particularly whether it exists primarily within a cavity or encompasses interior water molecules, has been the subject of much recent debate. In Paper I [C.-C. Zho et al., J. Chem. Phys. 147, 074503 (2017)], we found that mixed quantum/classical simulations with cavity and non-cavity pseudopotentials gave different predictions for the temperature dependence of the rate of the photoexcited hydrated electron's relaxation back to the ground state. In this paper, we measure the ultrafast transient absorption spectroscopy of the photoexcited hydrated electron as a function of temperature to confront the predictions of our simulations. The ultrafast spectroscopy clearly shows faster relaxation dynamics at higher temperatures. In particular, the transient absorption data show a clear excess bleach beyond that of the equilibrium hydrated electron's ground-state absorption that can only be explained by stimulated emission. This stimulated emission component, which is consistent with the experimentally known fluorescence spectrum of the hydrated electron, decreases in both amplitude and lifetime as the temperature is increased. We use a kinetic model to globally fit the temperature-dependent transient absorption data at multiple temperatures ranging from 0 to 45 C. We find the room-temperature lifetime of the excited-state hydrated electron to be 137±40 fs, in close agreement with recent time-resolved photoelectron spectroscopy (TRPES) experiments and in strong support of the "non-adiabatic" picture of the hydrated electron's excited-state relaxation. Moreover, we find that the excited-state lifetime is strongly temperature dependent, changing by slightly more than a factor of two over the 45C temperature range explored. This temperature dependence of the lifetime, along with a faster rate of ground-state cooling with increasing bulk temperature, should be directly observable by future TRPES experiments. Our data also suggest that the red side of the hydrated electron's fluorescence spectrum should significantly decrease with increasing temperature. Overall, our results are not consistent with the nearly complete lack of temperature dependence predicted by traditional cavity models of the hydrated electron but instead agree qualitatively and nearly quantitatively with the temperature-dependent structural changes predicted by the non-cavity hydrated electron model.

show abstract

Section: A Modeling the Hydrated Electron's Lifetime With Transient mentioning

confidence: 95%

Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

Farr

Zho

Challa

et al. 2017

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…In spite of this correction, the original octahedral model persists, and molecular dynamics simulations 3 with this configuration indeed captured most aspects of transient absorption spectra of solvated electrons 4 . Recent resonance Raman studies on aqueous solvated electrons 5,6 showed strongly enhanced, moderately red-shifted intramolecular bending and blue-shifted libration modes compared to bulk water and were also interpreted within the context of the original octahedral model. In this paper, we investigate electron hydration from a different perspective, namely the vibrational spectroscopy of water cluster anions (H 2 O) n -.…”

Section: Manuscriptmentioning

confidence: 91%

Vibrational spectroscopy of hydrated electron clusters(H2O)15–50− via infrared multiple photon dissociation

Asmis

Santambrogio

Zhou³

et al. 2007

The Journal of Chemical Physics

View full text Add to dashboard Cite

Infrared multiple photon dissociation spectra for size-selected water cluster anions (H2O)n−, n=15–50, are presented covering the frequency range of 560–1820cm−1. The cluster ions are trapped and cooled by collisions with ambient He gas at 20K, with the goal of defining the cluster temperature better than in previous investigations of these species. Signal is seen in two frequency regions centered around 700 and 1500–1650cm−1, corresponding to water librational and bending motions, respectively. The bending feature associated with a double-acceptor water molecule binding to the excess electron is clearly seen up to n=35, but above n=25; this feature begins to blueshift and broadens, suggesting a more delocalized electron binding motif for the larger clusters in which the excess electron interacts with multiple water molecules.

show abstract

“…The experiments by Tauber and Mathies (6,8) and Tahara and coworkers (30) found that the water vibrations that were resonantly enhanced upon excitation of the hydrated electron were virtually identical to those of bulk liquid water, indicating that the hydrated electron's wave function resides predominantly between water molecules and does not significantly perturb the water's electronic structure. The resonance Raman spectrum of water associated with the hydrated electron does show a slight red shift of the bending vibration and a broadening and enhancement on the red side of the O-H stretching vibration; the experimental data from ref.…”

Section: Modeling the Resonance Raman Spectrum Of The Hydrated Electronmentioning

confidence: 99%

Resonance Raman and temperature-dependent electronic absorption spectra of cavity and noncavity models of the hydrated electron

Casey

Larsen

Schwartz

2013

Proc. Natl. Acad. Sci. U.S.A.

135

View full text Add to dashboard Cite

Most of what is known about the structure of the hydrated electron comes from mixed quantum/classical simulations, which depend on the pseudopotential that couples the quantum electron to the classical water molecules. These potentials usually are highly repulsive, producing cavity-bound hydrated electrons that break the local water H-bonding structure. However, we recently developed a more attractive potential, which produces a hydrated electron that encompasses a region of enhanced water density. Both our noncavity and the various cavity models predict similar experimental observables. In this paper, we work to distinguish between these models by studying both the temperature dependence of the optical absorption spectrum, which provides insight into the balance of the attractive and repulsive terms in the potential, and the resonance Raman spectrum, which provides a direct measure of the local H-bonding environment near the electron. We find that only our noncavity model can capture the experimental red shift of the hydrated electron's absorption spectrum with increasing temperature at constant density. Cavity models of the hydrated electron predict a solvation structure similar to that of the larger aqueous halides, leading to a Raman O-H stretching band that is blue-shifted and narrower than that of bulk water. In contrast, experiments show the hydrated electron has a broader and red-shifted O-H stretching band compared with bulk water, a feature recovered by our noncavity model. We conclude that although our noncavity model does not provide perfect quantitative agreement with experiment, the hydrated electron must have a significant degree of noncavity character.solvated electron | quantum simulation | Raman spectroscopy | optical spectroscopy T he hydrated electron is the simplest quantum mechanical solute, consisting of an excess electron in liquid water. Because of its apparent simplicity, the hydrated electron provides a unique opportunity for confrontation between experiments and quantum simulations. However, despite nearly five decades of interest in the hydrated electron, there is still controversy over the nature of its molecular structure (1-14). Experimental observables, such as the absorption spectrum of the hydrated electron at different temperatures and pressures (12, 13) or the results of ultrafast pump-probe experiments on the hydrated electron, provide only indirect clues to the electron's molecular structure. One of the few experiments that offered a definite possible structure was electron spin-echo envelope modulation measurements on excess electrons in aqueous alkaline glassy matrices at 77 K (1). These experiments suggested that the electron is localized in a cavity that contains no water molecules, and that there are six surrounding water molecules in an octahedral geometry around the cavity, each with an O-H bond oriented toward the electron; this arrangement has been referred to as the "Kevan structure." It is not clear, however, how transferrable results from frozen aqueous alkaline...

show abstract

Novel Resonance Raman Enhancement of Local Structure around Solvated Electrons in Water

Cited by 41 publications

References 23 publications

Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

Temperature dependence of the hydrated electron’s excited-state relaxation. II. Elucidating the relaxation mechanism through ultrafast transient absorption and stimulated emission spectroscopy

Vibrational spectroscopy of hydrated electron clusters(H2O)15–50− via infrared multiple photon dissociation

Resonance Raman and temperature-dependent electronic absorption spectra of cavity and noncavity models of the hydrated electron

Contact Info

Product

Resources

About