"Initial" spectra of trapped electrons in alcohol glasses from 12 to 115 K

Klassen, Norman V.; Teather, George G.

doi:10.1021/j100243a021

Cited by 12 publications

(1 citation statement)

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“…Alcohols (1)(2)(3)(4)(5) and alcohol/water mixtures (6,7) have been particularly informative about the sensitivity of the spectrum to changes of internal structure of the liquid. In these liquids, structure changes occur because of the interplay between nonpolar and hydrogen-bonding groups.…”

Section: Introductionmentioning

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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