Mass analyzed threshold ionization spectroscopy of 1-methylindole cation

• Published in: Chemical physics letters Vol. 377; no. 5; pp. 620 - 626
• Main Authors: Lin, Jung Lee, Tzeng, Wen Bih
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 22.08.2003; Elsevier Science
• Subjects: Atomic and molecular physics; Autoionization, photoionization, and photodetachment; Exact sciences and technology; Molecular properties and interactions with photons; Photon interactions with molecules; Physics; Vibronic states; Energy levels; Ground states; Supersonic beam; Nitrogen heterocycle; Theoretical study; Experimental study; Photoionization; Vibrational modes; Density functional method; Ionization potential; Electronic transition; Ab initio calculations; Indole derivatives; Mass spectra; Organic compounds
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/S0009-2614(03)01205-3

The vibrationally resolved mass analyzed threshold ionization spectra of jet-cooled 1-methylindole (1MI) have been recorded by ionizing via four vibronic levels. The adiabatic ionization energy of this molecule is determined to be 60 749 ± 5 cm −1, which is less than that of indole by 1842 cm −1. This indicates that the N-methyl substitution causes a greater extent of the lowering in the zero energy level of the cationic ground state than that of the neutral. A few characteristic vibrations of the 1MI cation are observed, where the frequencies of the out-of-plane, in-plane bending and stretching vibrations of the N–CH 3 part are found to be 124, 251, and 1492 cm −1, respectively.