ABSTRACT
The advent of femtosecond spin dynamics was in 1996, when it was first shown that laser pulses can induce demagnetization in extended ferromagnetic systems. Today research has come a long way from considering magnetic materials solely for information storage, but even in this particular research area smaller clusters are more appealing than larger ones. Quantum chemical calculations can do more than describe the experimental electronic absorption spectra. Quantum chemical theories can also very successfully describe infrared spectra, and thus help characterize structures and isomers, which is a prerequisite to identify suitable ultrafast phenomena. The implementation of spin-based logic in a real device necessitates one more ingredient, not discussed until now: preparing the system for the computation. This means that the system must be put to a specific electronic and/or magnetic state, regardless of the state it is in. This chapter presents some concepts which are pertinent to the ultrafast spin dynamics of molecular magnets, in particular laser-induced spin dynamics.
