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2. Decoherence in Condensed Phase Nonadiabatic Dynamics
How to include decoherence into a time-domain atomistic simulation?
- Why is it an issue? Examples
- Simple measures of decoherence
How to justify (derive) models used for this purpose?
Is there something between system-bath and explicit atomistic models?

3. Example: Solvated Electron
- Cannot get away with a harmonic bath model
Without decoherence 600 fs P-S transition time
becomes <10fs

4. Example: Solvated Electron
- Cannot get away with a harmonic bath model
Without decoherence 600 fs P-S transition time
becomes <10fs
- Decoherence explains absence of solvent isotope effect

5. Decoherence and Quantum-Classical Simulation
Reduced density matrix:
on decoherence
time scale, missing
in q.-cl. models
With decoherence:
Without decoherence
Decoherence makes transitions less likely
(quantum Zeno effect)

6. Simple Estimates of Decoherence Time
Bath (vibrational) wave functions diverge
Method 1. Assume is particle is a Gaussian wave packet
too simplistic, what width to use?
Method 2. Compute the correlation function
what if properties change with time?

7. Another Problem that can be Resolved by Decoherence
Single average
trajectory
is unphysical
Instead chemists
designed ad hoc
surface hopping

8. Another Problem that can be Resolved by Decoherence
Stochastic Schrodinger
equation gives branching
- decoherence rate, L - system-bath coupling
Bath is present twice (in H and L) ??

9. Separate Classical Variables and Treat Quantum Variables as Bath= q 2 + 3
forming infinite hierarchy
Can higher orders in this recursive map be described
stochastically?

10. Spin-Phonon Example classical energy decreases
Most energy transfers into quantum variables
and spin becomes chaotic

11. Classical energy fluctuates at some “temperature” ??
Spin-Phonon Example
Classical energy fluctuates at some “temperature” ??

12. Decoherence in Condensed Phase Nonadiabatic Dynamics
How to include decoherence into a time-domain atomistic simulation?
- Why is it an issue? Examples
- Simple measures of decoherence
How to justify (derive) models used for this purpose?
Is there something between system-bath and explicit atomistic models?