Temperature shifts in the optical spectra of solvated electrons in methanol and ethanol

Jha, K.N.; Bolton, Gerald L.; Freeman, Gordon R.

doi:10.1021/j100669a034

Cited by 77 publications

(49 citation statements)

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“…First, our studies show no evidence for photoionization, an alternate channel available for aromatics excited above the likely threshold for adiabatic ionization in polar solvents. 39 Photoionization of p-MePhSH is ruled out from our results as no transients associated with p-MePhSH + cations, which have been characterized to absorb at 550 nm in n-butyl-chloride, 36 or solvated electrons 40,41 Our TA data also show spectral narrowing of the p-MePhS( X ) radical product over longer time delays, as the initially hot radicals dissipate their energy into the solvent bath on a picosecond timescale. Although differing widths in the nascent p-MePhS( X ) electronic absorption can be observed, most notably in our previous study employing 200 nm excitation, 16,17 this vibrational cooling is more easily quantified in UV-IR pump-probe data as there are far fewer overlapping features in the mid-infrared probe region.…”

Section: Discussionmentioning

confidence: 63%

Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol

et al. 2013

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A wavelength-resolved ( pump = 295, 285, 270 and 267 nm) photodissociation study of paramethylthiophenol (p-MePhSH) in ethanol solution has been performed using femtosecond transient absorption (TA) spectroscopy and the results compared with those from studies of the corresponding photodissociation in cyclohexane solution at 270 nm. Anisotropy spectra are used to identify the electronic character of the initially populated excited state(s). S-H bond fission is found to occur via the dissociative S 2 (1 1 πσ*) state, which can be populated directly, or by ultrafast non-radiative transitions from the S 3 (2 1 ππ*) state, or by very efficient tunneling from the S 1 (1 1 ππ*) state, depending on the excitation wavelength -in line with conclusions from

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Section: Discussionmentioning

confidence: 63%

Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol

et al. 2013

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“…24 From the increase of the absorbance at 340 nm during the first 50 ns after the pulse compared to the decrease of e -solv at 620 nm, we derive (Ag 0 ) ) 9.6 × 10 3 M -1 cm -1 .…”

Section: G(nag Nmentioning

confidence: 93%

Transient and Stable Silver Clusters Induced by Radiolysis in Methanol

et al. 2002

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The optical absorption spectra of Ag 0 , Ag 2 + , transient oligomers, and stable clusters were studied in deaerated methanol by pulse and γ-radiolysis methods and compared with data obtained from studies using other solvents. From the decay of esolv at 620 nm, the formation rate constant of Ag 0 was determined to be k(esolv + Ag + ) ) (2.6 ( 0.6) × 10 10 M -1 s -1 . The coalescence rate of transient oligomers is particularly slow and the growth process is not completed within 2 s after the pulse. The surface plasmon band of stable clusters obtained by γ-radiolysis in methanol is intense and sharp ( 385 nm ) 1.8 × 10 4 M -1 cm -1 ). The clusters are readily oxidized by oxygen. By adding methyl viologen MV 2+ to the solution containing stable silver clusters, the blue color of MV +• is transitorily observed, and the small clusters are developed into larger ones. Similarly, by pulse radiolysis of a mixture of silver cations and MV 2+ , silver atoms and MV +• are formed immediately through solvated electron scavenging, but subsequently additional MV +• are produced by reduction of MV 2+ by Ag 0 and small oligomers. In a further step, MV +• radicals reduce Ag + cations adsorbed on large clusters and let them develop eventually to larger sizes. The general mechanism of the methanol radiolysis is revisited on the basis of electron and radical scavenging by Ag + and silver clusters, and values of the yields of methanol radiolysis species are discussed in detail.

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“…The cell was then sealed with a flame by a technique that prevented diol vapor from contacting the hot glass (9).…”

Section: Methodsmentioning

confidence: 99%

Temperature and molecular structure dependences of optical spectra of electrons in liquid diols

Okazaki¹,

Idriss-Ali²,

Freeman³

1984

Can. J. Chem.

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at 215 K the optical spectrum of e-, shifted unsymmetrically towards higher energy the first 500 ns. Approximating the decay of the low energy side and the growth of the high energy side of the band as first order, the mean decay time at 0.5EA,,. (e-,) was T, = 160 ns and the mean growth time at E > E A ,~~ (e-5) was T, = 40 ns. The behavior in 1,3-butanediol (13BD) at 225 K was similar, with T~ = 170 ns at 0.5EAm,, and T , = 40 ns at E > EAmax. The solvation time constant T, is only slightly greater than 7,. The larger value of T~ is caused by replenishment of the state at 0.5EA,,, by relaxation from lower energy states. In all diols at T 2 240 K (2298 K for 14BD) the spectra reached their equilibrium shape within 150 ns after the start of the 100 ns radiation pulse. The value of EAm, , of e-, in the 1 ,2-diols is -0.1 eV greater than those in the other diols and 0.2-0.3 eV greater than that in a primary alcohol at the same temperature. In the secondary-secondary diol 23BD at 296 K, EAmnx is 0.6 eV greater than that in 2-propanol. The vicinal diol part of the molecule dominates the intermolecular solvation site of the electron. The temperature coefficient (-dE~,,,ldT) increases from 2.6 meV/K in 12 ED to 3.6 meV/K in 23BD. The asymmetry factors Wb/Wr of the e-, bands in the diols are 1.6-2.1, somewhat lower than those in the analogous alcohols, 1.9-2.4. The values of W, are similar, 0.54 k 0.04 eV, in all the diols, independent of T, with Wr/EA,,, = 0.24 + 0.02; dWb/dT < 1.0 meV/K. The value of (GE),,, has an upper limit of -2.5 X lo4 e-,/lo0 eV M cm in the low temperature liquid diols. The value of go^,,, is 1.2 X lo4 in all diols except 23BD, in which it is 1.3 x lo4, independent of T. Dans le propanediol-1,2 (PD12), a 215 K, le spectre optique des e-, glisse d'une faqon non symCtrique vers les hautes Cnergies pendant les 500 premikres nanosecondes. En faisant I'hypothkse que la dCcroissement du c8tC de faible Cnergie et que la croissance du cBtC de haute Cnergie de la bande sont d'ordre un, le temps moyen de dCcroissement a 0,5EA,,, (e-,) est T, = 160 ns et le temps moyen de croissance a E > E, , . , (e-,) est de T , = 40 ns. A 225 K, le butanediol-1,3 (BD13) se comporte de la m&me faqon et T, = 170 ns a 0,5EA,,, et T , = 40 ns a E > EAmax La constante de temps de solvatation T, n'est que 1Cgkrement sup6rieure a 7 , . La valeur plus ClevCe de T , est due au remplissage de 1'Ctat a 0,5EA,,, par une relaxation des Ctats de plus faible Cnergie. Dans tous les diols, a des T 2 240 K (2298 K pour le BD14), les spectres atteignent leur forme d1Cquilibre en moins de 150 ns aprks le dCbut de la radiation pulsCe de 100 ns. A des tempCratures constantes, la valeur de EAmax des e-,, dans les diols-1,2, est sup6rieure d'environ 0,l eV a celles observCes avec d'autres diols et de 0,2 0,3 eV sup6rieure a celle observke dans un alcool primaire. Dans le diol secondaire-secondaire (BD23), a 296 K, la valeur de E,,,, est de 0,6 eV sup6rieure a celle observke dans le propanol-2. La portion viccinale de la molCcule de diol domin...

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Temperature shifts in the optical spectra of solvated electrons in methanol and ethanol

Cited by 77 publications

References 8 publications

Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol

Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol

Transient and Stable Silver Clusters Induced by Radiolysis in Methanol

Temperature and molecular structure dependences of optical spectra of electrons in liquid diols

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