Fluorescence excitation spectroscopy of the 3p Rydberg states of 1-azabicyclo[2.2.2]octane and 1-azaadamantane

The singlet states of the 3p Rydberg manifold of the structurally rigid ami nes 1-azabicyclo[2.2.2] octane and 1-azaadamantane seeded in supersonic exp ansions have been investigated by means of fluorescence excitation spectros copy. Under these conditions a better spectral resolution could be obtained than in previous studies, enabling us to resolve and identify unambiguousl y the 0(0)(0) transitions to the second and third excited singlet states. T hese states are assigned as the 1(1)E and 3(1)A(1) states, associated with excitation of a lone-pair electron to the 3p(x,y) and 3p(z) Rydberg orbital s, respectively. Analysis of the vibrational energies and intensities of vi bronic transitions observed in the excitation spectra of both states leads to the conclusion that the equilibrium geometry and vibrational properties of the molecule in these two states resemble closely those of the lowest ex cited singlet state, which derives from excitation of a lone-pair electron to the 3s Rydberg orbital, and those of their ionic core. Excitation spectr a in combination with dispersed emission spectra and fluorescence decays de monstrate that internal conversion to the lowest excited singlet state show s up prominently in the dynamics of the 3p Rydberg states.