We present a computational study of the one-photon and excited-state absorption from the two lowest-energy excited states of uracil in the gas phase: an n?pi* dark state<br>(1n) and the lowest-energy bright ??? pi-pi* state (1?pi). The predictions of six di?fferent linear response electronic structure methods, namely TD-CAM-B3LYP, EOM-CCSD,<br>EOM-CC3, ADC(2), ADC(2)-x and ADC(3) are critically compared. In general, the spectral shapes predicted by TD-CAM-B3LYP, EOM-CCSD, EOM-CC3 and ADC(3) are fairly similar, though the quality of TD-CAM-B3LYP slightly deteriorates in the high energy region. Computing the spectra at some key structures on the di?fferent potential energy surfaces (PES), i.e. the Franck-Condon point, the 1n minimum,<br>and structures representative of di?fferent regions of the 1? PES, we obtain important insights into the shift of the excited-state absorption spectra, following the motion of the<br>wavepacket on the excited state PES. Though 1pi ? has larger excited-state absorption than 1n, some spectral regions are dominated by these latter signals. Aside from its<br>methodological interest, we thus obtain interesting indications to interpret transient absorption spectra to disentangle the photoactivated dynamics of nucleobases.
Excited State Absorption of Uracil in the Gas Phase: Mapping the Main Decay Paths by Different Electronic Structure Methods
