Photoinduced Electron Transfer and Solvation in Iodide-doped Acetonitrile Clusters

Ehrler, Oli T.; Griffin, Graham B.; Young, Ryan M.; Neumark, Daniel M.

doi:10.1021/jp806856m

Cited by 23 publications

(40 citation statements)

References 51 publications

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“…These assignments explain the complementary time-dependence of features A and B, since the excited state either undergoes autodetachment or is photodetached by the probe pulse. 46,47 For all sizes studied here, both the peak and width of the eKE distribution for feature B change significantly with pump-probe delay, with the extent of this variation changing with cluster size. Partial (-d1) and full (-d4) deuteration result only in small effects on the timedependent intensities, binding energies, and spectral shapes.…”

Section: Resultsmentioning

confidence: 87%

“…Based on our previous work on I − (H 2 O) n and I − (CH 3 CN) n clusters, 46,47 we assign feature A to VAD of the I − (CH 3 OH) n clusters after pump excitation. Likewise, feature B is assigned to the [1+1 ] pump-probe signal from the excited state of the cluster.…”

Section: Resultsmentioning

confidence: 99%

“…Equation (3) is a phenomenological lineshape that has been observed previously for halidesolvent clusters. 47 The FWHM of the kinetic energy profile is (w 1 + w 2 ) × √ ln 2. For n = 4 only, where direct detachment leading to features C and D competes with CTTS excitation, the eKE spectrum at t = -1 ps is first subtracted before fitting to avoid contamination.…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Young

Yandell

Neumark

2011

The Journal of Chemical Physics

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The dynamics of electron solvation following excitation of the charge-transfer-to-solvent precursor state in iodide-doped methanol clusters, I(-)(CH(3)OH)(n = 4-11), are studied with time-resolved photoelectron imaging. This excitation produces a I···(CH(3)OH)(n)(-) cluster that is unstable with respect to electron autodetachment and whose autodetachment lifetime increases monotonically from ~800 fs to 85 ps as n increases from 4 to 11. The vertical detachment energy (VDE) and width of the excited state feature in the photoelectron spectrum show complex time dependence during the lifetime of this state. The VDE decreases over the first 100-400 fs, then rises exponentially to a maximum with a ~1 ps time constant, and finally decreases by as much as 180 meV with timescales of 3-20 ps. The early dynamics are associated with electron transfer from the iodide to the methanol cluster, while the longer-time changes in VDE are attributed to solvent reordering, possibly in conjunction with ejection of neutral iodine from the cluster. Changes in the observed width of the spectrum largely follow those of the VDEs; the dynamics of both are attributed to the major rearrangement of the solvent cluster during relaxation. The relaxation dynamics are interpreted as a reorientation of at least one methanol molecule and the disruption and formation of the solvent network in order to accommodate the excess charge.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Young

Yandell

Neumark

2011

The Journal of Chemical Physics

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“…55,56 We have studied CTTS dynamics in I -(CH 3 CN) n with 5 e n e 10 using TRPES. 57 The pump energies were 4.6 (n ) 5-8) and 5.1 eV (n ) 9, 10), and the probe photon energy was 1.56 eV. Spectra for n ) 5 are shown in Figure 10.…”

Section: Ctts Dynamics In I -(Ch 3 Cn) Nmentioning

confidence: 99%

Dynamics of Electron Solvation in Molecular Clusters

Ehrler

Neumark

2009

Acc. Chem. Res.

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S olvated electrons, and hydrated electrons in particular, are important species in condensed phase chemistry, physics, and biology. Many studies have examined the formation mechanism, reactivity, spectroscopy, and dynamics of electrons in aqueous solution and other solvents, leading to a fundamental understanding of the electron-solvent interaction. However, key aspects of solvated electrons remain controversial, and the interaction between hydrated electrons and water is of central interest. For example, although researchers generally accept that hydrated electrons, e aq -, occupy solvent cavities, another picture suggests that the electron resides in a diffuse orbital localized on a H 3 O radical. In addition, researchers have proposed two physically distinct models for the relaxation mechanism when the electron is excited. These models, formulated to interpret condensed phase experiments, have markedly different time scales for the internal conversion from the excited p state to the ground s state.Studies of negatively charged clusters, such as (H 2 O) n -and I -(H 2 O) n , offer a complementary perspective for studying aqueous electron solvation. In this Account, we use time-resolved photoelectron spectroscopy (TRPES), a femtosecond pump-probe technique in which mass-selected anions are electronically excited and then photodetached at a series of delay times, to focus on time-resolved dynamics in these and similar species. In (H 2 O) n -, TRPES gives evidence for ultrafast internal conversion in clusters up to n ) 100. Extrapolation of these results yields a p-state lifetime of 50 fs in the bulk limit. This is in good agreement with the nonadiabatic solvation model, one of the models proposed for relaxation of e aq -. Similarly, experiments on (MeOH) n -up to n ) 450 give an extrapolated p-state lifetime of 150 fs.TRPES investigations of I -(H 2 O) n and I -(CH 3 CN) n probe a different aspect of electron solvation dynamics. In these experiments, an ultraviolet pump pulse excites the cluster analog of the charge-transfer-to-solvent (CTTS) band, ejecting an electron from the iodide into the solvent network. The probe pulse then monitors the solvent response to this excess electron, specifically its stabilization via solvent rearrangement. In I -(H 2 O) n , the iodide sits outside the solvent network, as does the excess electron initially formed by CTTS excitation. However, the iodide in I -(CH 3 CN) n is internally solvated, and both experimental and theoretical evidence indicate that electrons in (CH 3 CN) n -are internally solvated. Hence, these experiments reflect the complex dynamics that ensue when the electron is photodetached within a highly confined solvent cavity.

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“…Many detection schemes have been developed to combine with the pump-probe technique to explore the dynamics of neutral molecules in the gas phase [4]. For molecular anions, a few methods have been successfully demonstrated [5][6][7][8]. By contrast, very few examples are known for the time-resolved studies of molecular cations on the fs time scale [9].…”

Section: Introductionmentioning

confidence: 99%

Femtosecond pump-probe photoionization-photofragmentation spectroscopy of azobenzene cation

Chen

Cheng

2010

Sci. China Phys. Mech. Astron.

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We report the studies of ultrafast dynamics of azobenzene cations using femtosecond photoionization-photofragmentation spectroscopy. In our experiment, a femtosecond pump pulse first prepares an ensemble of azobenzene cations via photoionization of neutrals. A delayed probe pulse then brings the evolving ionic system to higher states that ultimately undergo ion fragmentation. The dynamics is followed by monitoring either the parent-ion depletion or fragment-ion formation as a function of the pump-probe delay time. The observed transients for azobenzene cations are characterized by a constant ion depletion modulated by a rapidly damped oscillatory signal with a period of about 1 ps. Theoretical calculations suggest that the oscillation arises from a vibration motion along the twisting inversion coordinate involving displacements in CNNC and phenyl-ring torsions. The oscillation is damped rapidly with a time constant of about 1.2 ps, suggesting that energy dissipation from the active mode to bath modes takes place on this time scale. femtosecond laser, wave packet, azobenzene, photoisomerization PACS: 82.53.-k, 82.30.-b

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Photoinduced Electron Transfer and Solvation in Iodide-doped Acetonitrile Clusters

Cited by 23 publications

References 51 publications

Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Dynamics of electron solvation in I−(CH3OH)n clusters (4 ≤ n ≤ 11)

Dynamics of Electron Solvation in Molecular Clusters

Femtosecond pump-probe photoionization-photofragmentation spectroscopy of azobenzene cation

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