"The interaction between UV light and DNA molecules has been a very attractive research field because of not only the pharmaceutical relevance for UV-induced cancer problems but also the unique ultrafast dynamics of these photochemical systems. DNA molecules have undergone natural selection for millennia, but despite that evolution, their strong absorption of harmful UV light and their critical role in the reproduction of genetic information would seem to be irreconcilable properties. However, the relatively recent discovery that they undergo ultrafast nonradiative decay after absorbing UV light and thereby rapidly quench the excited state and prevent photodamage explains their photostability under UV irradiation. Ultrafast energy dissipation mechanism of DNA helps its photochemistry be very stable despite of countless interaction with sunlight. Spectroscopic tools to monitor ultrafast photo-induced events have become more prevalent and accurate as femtosecond laser techniques have been progressively developed. Until now, the applied methodologies have been inclined to monitor the lifetimes of excited states by femtosecond transient absorption and fluorescence up-conversion spectroscopy because they detect signals using the large cross-sections of electronic transitions. However, how the vibrational structures of excited-state DNA change during the ultrafast energy deactivation event is poorly studied. Here, we investigate this structural picture of the ultrafast dynamics of DNA with femtosecond stimulated Raman spectroscopy (FSRS). FSRS has been a very powerful time-resolved vibrational spectroscopy to monitor structural changes during ultrafast excited-state dynamics. To overcome inherently weak Raman signal, we utilized resonance Raman enhancement to boost the signal intensity with UV and visible Raman pump pulses generated by our whitelight-seeded stimulated Raman shifter with high-pressure hydrogen gas. In UV-resonance FSRS of DNA base monomers, hot ground-state vibrations were not observed but very broad vibrations with time constants comparable with excited-state lifetime were weakly shown in dGMP. In visible-resonance FSRS of dGMP, the broad linewidth signals were consistently observed more clearly with resonance Raman enhancement. The results from the resonance FSRS of dGMP indicate that dGMP assumes a broad distribution of out-of-plane structures during the ultrafast evolution on the excited-state potential energy surface"--Pages ix-xi