RESUMO
A model Hamiltonian based on the vibronic coupling model is developed to describe the excited state dynamics of 3-pyrroline. With the use of the method of improved relaxation in conjunction with the MCTDH wavepacket propagation algorithm, vibrational eigenstates corresponding to both the axial and equatorial conformers of 3-pyrroline are calculated and subsequently used in a conformer-resolved study of the photodissociation of 3-pyrroline following excitation to its S1(3s/πσ*) and S2(3px) states. In analogy with ammonia, the excited state dynamics of both conformers of 3-pyrroline are found to be dominated by the (quasi-) planarization of the molecule in its electronically excited states and predominantly diabatic behavior of dissociation mediated by a conical intersection between the S1 and S0 states.
RESUMO
The first band in the electronic spectrum of pyrrole is calculated from wavepacket propagations performed using the MCTDH method. To do so, two model Hamiltonians are constructed to describe seven low-lying excited electronic states of pyrrole. These Hamiltonians are based on the vibronic coupling model, and are parameterised via fitting to extensive CASPT2 and EOM-CCSD calculations. A detailed analysis of the structure of pyrrole's electronic spectrum in the range 5.5 to 6.5 eV is made. The role of intensity borrowing from transitions to ππ(*) states by lower-lying 3s and 3p Rydberg states is assessed, and reassignments of much of the spectrum are subsequently made which indicate that most of the states in the spectrum are predominantly Rydberg in character. The resulting conclusions drawn serve to highlight the limitations of assignments based on the matching of calculated vertical excitation energies and the positions of peak maxima observed in electronic spectra.
RESUMO
A model Hamiltonian based on the quadratic vibronic coupling model is developed to describe the photoinduced dynamics of aniline excited to the manifold of states comprising its first six singlet electronic states. The model Hamiltonian is parametrized by fitting to the results of extensive EOM-CCSD calculations and its validity tested through the calculation of the first two bands in the electronic absorption spectrum of aniline. It is found that two previously neglected 3p Rydberg states play an important role in the dynamics of aniline following excitation into the first two (1)ππ* states. Assignments of the vibrational structure seen in the experimental spectrum is made, and the role played by the Herzberg-Teller effect in excitation to the first (1)ππ* state is analyzed.
RESUMO
The geometric structures of small cationic rhodium clusters Rh(n)(+) (n = 6-12) are investigated by comparison of experimental far-infrared multiple photon dissociation spectra with spectra calculated using density functional theory. The clusters are found to favor structures based on octahedral and tetrahedral motifs for most of the sizes considered, in contrast to previous theoretical predictions that rhodium clusters should favor cubic motifs. Our findings highlight the need for further development of theoretical and computational methods to treat these high-spin transition metal clusters.