Ultrafast photo-excited dynamics are of great importance in a myriad of fundamental natural processes, such as, vision, photostability of nucleobases, photosynthesis, etc. We propose to simulate such dynamics and explain the relaxation pathway of the excited electronic energy in small organic molecules where excited state intramolecular hydrogen transfer occurs in an ultrafast manner. The computational time will be used to perform ab initio multiple spawning dynamics simulations coupled to high-level multireference electronic structure methods, to understand the mechanism and calculate timescales of internal conversion and intersystem crossing processes in those molecules. Our simulations, in conjunction with time-resolved X-ray absorption and scattering spectroscopies performed by our experimental collaborators, will allow for a clear picture of light-induced dynamics in such molecules.