The photophysics of tertiary aliphatic amines

Electronic Spectroscopy and Ultrafast Energy Relaxation Pathways in the Lowest Rydberg States of Trimethylamine

“…Even using a narrow bandwidth picosecond laser, the 3p levels are still unresolved (data not shown), indicating the resolution limit is approximately 50 meV or more at this photon energy. Excitation at 209 nm leads almost exclusively to 3p 9. Ionization out of 3s is nonetheless observed because the far UV laser pulses are temporally broadened by dispersive optical elements.…”

“…As had been observed in absorption,2 the MRES exhibits no clear vibrational structure in trimethylamine, and the most prominent feature, a peak near 44,000 cm -1 excitation energy, is difficult to assign due to the overlap of the 3s and 3p Rydberg states in this region 9…”

“…They all feature pyramidal ground electronic states and planar Rydberg excited states, and they have internal rotations associated with the methyl groups 2. The smallest tertiary amine, trimethylamine (TMA), N(CH 3 ) 3 , has been used as a prototype to explore the spectroscopy and photochemistry of this class of compounds 9,10,11. Among the amines, the tertiary amines have the lowest ionization energies,12 causing the Rydberg series to start at a relatively low energy, about 4.5 eV.…”

“…The absorption spectrum features a broad band between 250 and 220 nm that is assigned to the $3S\leftarrow n_N(\tilde{A}{}^{1}A_2^{″}\leftarrow \tilde{X}{}^{1}A_1)$ transition 2,9. Halpern et al used very high quality absorption spectra and a second derivative analysis technique to identify the vibrational progressions within this $\tilde{A}\leftarrow \tilde{X}$ transition 16.…”

Photodissociating trimethylamine at 193 nm to probe dynamics at a conical intersection and to calibrate detection efficiency of radical products

“…Two studies have observed fluorescence from S 1 to S 0 following excitation to the S 1 state and at excitation energies where the S 2 and S 1 absorptions overlap. 10,11 The authors of these papers reach different conclusions about the distribution of population in vibrational levels of the S 1 state, but in spite of these conflicting interpretations, both studies concur that rapid internal conversion from the S 2 to the S 1 state occurs. Because of the similarity of fluorescence spectra over the range of excitation wavelengths, it seems reasonable to assume that the S 2˜S 1 internal conversion is occurring near the Franck-Condon region.…”