Nonadiabatic molecular quantum dynamics

6 problems

• Lifetime of electronic coherence after sudden ionization of molecules

  Open

  An ultrashort laser pulse can knock out an electron and leave the remaining charge sloshing across the molecule within a few femtoseconds (millionths of a billionth of a second). How long this sloshing survives once the atoms start to move is not known.

• Vibrational energy loss of NO molecules colliding with gold

  Contested

  Highly vibrating NO molecules bouncing off a gold surface lose most of their vibration by exciting electrons in the metal. The two main theories disagree with each other and with the measured amount of energy lost.

• Charge transport mechanism in high-mobility organic semiconductors

  Open

  In organic crystals such as rubrene, charges move in a way that fits neither the picture of free electrons in a metal nor that of hops between fixed molecules. A complete theory that predicts the measured mobility (how fast charges drift in an electric field) is missing.

• Predictive accuracy of ab initio photochemical quantum yields

  Open

  A photochemical quantum yield is the fraction of absorbed photons that produce a given product. Current simulations cannot yet predict these fractions reliably before an experiment is done.

• A consistent trajectory method for coupled electron-nuclear dynamics

  Open

  Fully quantum simulation of molecules is too expensive, so chemists move atoms along classical paths and let them hop between electronic states. Existing recipes are ad hoc and fail in known test cases.

• Predictive photochemistry through conical intersections in solution and proteins

  Open

  After absorbing light, a molecule often returns to its lowest energy state through a conical intersection (a point where two electronic energy surfaces touch), and this step decides what product forms. Simulations can follow this in isolated molecules, but predicting yields and timings for molecules in liquids or proteins from first principles is not yet reliable.