Modeling two photon absorption cross sections of open-shell systems.

We demonstrate the prospects of computing two photon absorption cross sections of open-shell systems by applying recently developed spin-restricted time-dependent density functional response theory using the pyrrole radical as an example. The spin multiplicity effects on two photon absorption cross sections of this species are investigated for the doublet, quartet, and sextet states. It is found that irrespective of the exchange-correlation functional employed, the two photon cross sections increase with the increase in spin multiplicity. This result indicates that two photon cross sections of paramagnetic compounds can be controlled by manipulating their spin states and this opens new possibilities for design of hybrid magneto-optical materials.