Spherical symmetric diffusion problem

Krissinel, E.B.; Agmon, Noam

doi:10.1002/(sici)1096-987x(19960715)17:9<1085::aid-jcc1>3.3.co;2-t

Cited by 119 publications

(221 citation statements)

References 2 publications

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“…36 We solved eq 4 numerically, using a user-friendly Windows application for Spherically-Symmetric Diffusion Problems (SSDP, ver. 2.61) 37 to yield k(t) of eq 3.…”

Section: Discussionmentioning

confidence: 99%

Excited-State Proton Transfer in Methanol-Doped Ice in the Presence of KF

Uritski

Huppert

2008

J. Phys. Chem. A

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Steady-state and time-resolved emission techniques were employed to study the photoprotolytic cycle of an excited photoacid in ice in the presence of a low concentration of a weak base-like F(-). In previous studies we found that the photoprotolytic cycle in methanol-doped ice (1% mol fraction) is too slow to be observed at temperatures below 190 K. In this study we found that at temperatures below 240 K an additional proton-transfer process occurs in ice doped with 10 mM KF. We attributed this reaction to the creation of a mobile L-defect by F(-) ions. We used a diffusion-assisted reaction model, based on the Debye-Smoluchowski equation, to account for the direct reaction of the L-defect with the excited photoacid at temperatures below T < 240 K. Below 160 K the spectroscopic properties as well as the photoprotolytic cycle change dramatically. We propose that below 160 K the sample enters a new phase. The excited-state proton-transfer (ESPT) process was observed and followed down to a liquid nitrogen temperature of approximately 78 K. In the low-temperature phase the ESPT rate is almost twice as much as at 180 K and the temperature dependence of the rate is very small. The kinetic isotope effect of the ESPT at the low-temperature phase is small of about 1.3.

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“…36 We solved eq 4 numerically, using a user-friendly Windows application for Spherically-Symmetric Diffusion Problems (SSDP, ver. 2.61) 37 to yield k(t) of eq 3.…”

Section: Discussionmentioning

confidence: 99%

Excited-State Proton Transfer in Methanol-Doped Ice in the Presence of KF

Uritski

Huppert

2008

J. Phys. Chem. A

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“…In addition, considering the solvent effects, the conductor-like screening model (COSMO) was also used in all the calculations. 41, 42 The potential-energy curve of the The Journal of Physical Chemistry A…”

Section: ' Modeling Of the Tht Nonradiative Process Following The Glamentioning

confidence: 99%

Modeling the Nonradiative Decay Rate of Electronically Excited Thioflavin T

et al. 2011

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A computational model of nonradiative decay is developed and applied to explain the time-dependent emission spectrum of thioflavin T (ThT). The computational model is based on a previous model developed by Glasbeek and co-workers (van der Meer, M. J.; Zhang, H.; Glasbeek, M. J. Chem. Phys. 2000, 112, 2878) for auramine O, a molecule that, like ThT, exhibits a high nonradiative rate. The nonradiative rates of both auramine O and ThT are inversely proportional to the solvent viscosity. The Glasbeek model assumes that the excited state consists of an adiabatic potential surface constructed by adiabatic coupling of emissive and dark states. For ThT, the twist angle between the benzothiazole and the aniline is responsible for the extensive mixing of the two excited states. At a twist angle of 90°, the S(1) state assumes a charge-transfer-state character with very small oscillator strength, which causes the emission intensity to be very small as well. In the ground state, the twist angle of ThT is rather small. The photoexcitation leads first to a strongly emissive state (small twist angle). As time progresses, the twist angle increases and the oscillator strength decreases. The fit of the experimental results by the model calculations is good for times longer than 3 ps. When a two-coordinate model is invoked or a solvation spectral-shift component is added, the fit to the experimental results is good at all times.

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“…A code for the numerical solution of the spherically symmetric diffusion problem has been provided by Krissinel and Agmon. 25 We obtained a numerical solution to the diffusion equation using a radiative boundary condition at the contact radius, a pair interaction potential with minimum at the contact radius, and assumed all electrons started out in contact with the iodine atom. The position of the contact radius is again set to be 4 Å.…”

Section: A Nature Of the Caged Pairmentioning

confidence: 99%

Time-resolved scavenging and recombination dynamics from I:e− caged pairs

Kloepfer¹,

Vilchiz²,

Lenchenkov³

et al. 2002

The Journal of Chemical Physics

130

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The competition between geminate recombination of electrons with their parent radicals and electron scavenging with H+ is directly time resolved with ∼100 fs resolution at several acid concentrations. Electrons were produced from iodide photodetachment or two-photon ionization of H2O. With regards to those produced from iodide photodetachment, the separation between primary and secondary I:e− recombination is established using a full numerical solution to the diffusion equation. Electron ejection is found to be short range and a potential well of ∼3kbT depth stabilizing the solvent caged pair is required to yield a satisfactory fit to experiment. From time-resolved scavenging data up to 5 M HCl, it is shown that the electron can be scavenged both inside and outside the caged pair by H+ with nearly equal efficiency. The steady-state scavenging yield as a function of scavenger concentration is then predicted based on the determined time-dependent recombination function. Reassessment of several benchmark scavenging experiments from the 1960’s leads to the conclusion that the primary yield of electrons after excitation of iodide is near unity.

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Spherical symmetric diffusion problem

Cited by 119 publications

References 2 publications

Excited-State Proton Transfer in Methanol-Doped Ice in the Presence of KF

Excited-State Proton Transfer in Methanol-Doped Ice in the Presence of KF

Modeling the Nonradiative Decay Rate of Electronically Excited Thioflavin T

Time-resolved scavenging and recombination dynamics from I:e− caged pairs

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