Nonradiative electronic relaxation under collision-free conditions

The high-spin → low-spin relaxation in spin-crossover compounds can be described as non-adiabatic multi-phonon process in the strong coupling limit, in which the low-temperature tunnelling rate increases exponentially with the zero-point energy difference between the two states. Based on the hypothesis that the experimental bond length difference between the high-spin and the low-spin state of not, vert, similar0.2 Å is also valid for low-spin iron(II) complexes, extrapolation of the single configurational coordinate model allows an estimate of the zero-point energy difference for low-spin complexes from kinetic data. DFT calculations on low-spin [Fe(bpy)3]2+ support the structural assumption. However, for low-spin [Fe(terpy)2]2+ the relaxation rate constant shows an anomalous behaviour in so far as it is more in line with spin-crossover systems. This is attributed to very anisotropic bond length changes associated with the spin state change, and the subsequent breakdown of the single mode model

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“…In the two mode model the low-temperature tunnelling rate constant is given by [31] k HL (T → 0) = 2π…”

Section: A Notable Exception To the Rulementioning

confidence: 99%

Low-temperature lifetimes of metastable high-spin states in spin-crossover and in low-spin iron(II) compounds: The rule and exceptions to the rule

Hauser

Enachescu

Daku

et al. 2006

Coordination Chemistry Reviews

195

255

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“…1 Although conventional approaches such as fluorescence lifetime and quantum yield measurements provide fundamental information on deactivation processes, 2 direct observation of the nonstationary state is by far more informative for disentangling their complex dynamics. Recently-developed time-resolved photoelectron imaging technique [3][4][5][6] is extremely useful in this regard, since it provides the most sensitive and versatile means to probe both internal conversion and intersystem crossing processes through the observation of time-dependent energy and angular distributions of photoelectrons.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond photoelectron imaging of pyridazine: S1 lifetime and (3s(n−1),3p(n−1)) Rydberg state energetics

Matsumoto

Kim

Suzuki

2003

The Journal of Chemical Physics

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The first real-time study on pyridazine in the S 1 (n,*) state is presented. The S 1 state is found to dephase with a time constant of 323Ϯ17 ps at its origin, and the electronic dephasing mechanism is attributed to the S 1 -S 0 internal conversion. The S 1 lifetime is found to decrease rather sharply as the internal energy increases. The 3s (n Ϫ1 ) and 3 p (n Ϫ1 ) Rydberg states of pyridazine are clearly identified in angle-and energy-resolved photoelectron images obtained in the (1ϩ2Ј) photoionization scheme, providing their respective term values of 5.68Ϯ0.03 and 6.28Ϯ0.04 eV.

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“…8,9 The predicted gap between the ground and first electronically excited states is expected to function as a bottleneck for nonradiative relaxation to the ground state, in accord with the energy gap rule. 11 From these results, one expects that photoexcitation of cytosine or Al-cytosine to some of the higher energy states shown will be followed by efficient nonradiative relaxation (curve-crossing) events. Curve crossing from the first excited state to the ground state will be inefficient at near-equilibrium N-H bond lengths due to the relatively large energy gap between the two states.…”

Section: The Dehydrogenation Mechanismmentioning

confidence: 93%

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

2003

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Nonradiative electronic relaxation under collision-free conditions

Cited by 513 publications

References 47 publications

Low-temperature lifetimes of metastable high-spin states in spin-crossover and in low-spin iron(II) compounds: The rule and exceptions to the rule

Low-temperature lifetimes of metastable high-spin states in spin-crossover and in low-spin iron(II) compounds: The rule and exceptions to the rule

Femtosecond photoelectron imaging of pyridazine: S1 lifetime and (3s(n−1),3p(n−1)) Rydberg state energetics

Dehydrogenation and Other Non-radiative Relaxation Processes in Gas-Phase Metal−DNA Base Complexes

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