Performing photoinduced electron transfer (PET) calculations in Gaussian 09w involves setting up a computational model that describes the reactants, products, and the environment accurately. Here's a general guide on how to set up and run a PET calculation in Gaussian 09w.

Set up the molecular structures: Prepare the molecular structures of the donor, acceptor, and any other relevant molecules in a suitable molecular modeling software such as GaussView or Avogadro.

Optimize the geometry: Use Gaussian 09w to optimize the geometry of the reactants and products. This step ensures that the molecular structures are in their lowest energy state and ready for further calculations.

Specify the method and basis set: Choose an appropriate computational method and basis set for your PET calculation. Density Functional Theory (DFT) methods such as B3LYP or TD-DFT are commonly used for studying electronic transitions in molecules.

Set up the input file: Write an input file (.com) specifying the molecular coordinates, method, basis set, and any additional keywords required for your PET calculation. You may need to specify excited state calculations for TD-DFT calculations.

Thank you for your explanation. which keyword is used for PET, td(nstates=n) or excited state keyword td(nstates=n, root=n)