Vibrational and vibronic spectra of tryptamine conformers.

Conformation-specific ionization-detected stimulated Raman spectra, including both Raman loss and Raman gain lines, along with visible-visible-ultraviolet hole-burning spectra of tryptamine (TRA) conformers have been measured simultaneously, with the aim of obtaining new data for identifying them. The slightly different orientations of the ethylamine side chain relative to the indole lead to unique spectral signatures, pointing to the presence of seven TRA conformers in the molecular beam. Comparison of ionization-loss stimulated Raman spectra to computationally scaled harmonic Raman spectra, especially in the alkyl C-H and amine N-H stretch regions together with the retrieved information on the stabilities of the TRA conformers assisted their characterization and structural identification.

Simultaneous Ionization-Detected Stimulated Raman and Visible-Visible-Ultraviolet Hole-Burning Spectra of Two Tryptamine Conformers.

A key first step toward probing structures and interactions of individual conformers of isolated flexible molecules is uncovering their characteristic spectral signatures. Here, conformation-specific ionization-detected stimulated Raman (IDSR) and visible-visible-ultraviolet hole-burning spectra were measured simultaneously to determine the unique signatures of the two most stable conformers of tryptamine in the gas phase. These signatures together with the comparison of the IDSR spectra to the computationally predicted Raman spectra assisted in their characterization and structural identification.