Structural Dynamics in Floppy Systems: Ultrafast Conformeric Motions in Rydberg-Excited Triethylamine

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 115; no. 10; pp. 1804 - 1809
• Main Authors: Deb, Sanghamitra, Bayes, Brian A, Minitti, Michael P, Weber, Peter M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17.03.2011
• Subjects: A: Dynamics, Clusters, Excited States; Butylamines - chemistry; Ethylamines - chemistry; Kinetics; Models, Molecular; Molecular Conformation; Motion; Spectrum Analysis; Thermodynamics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp110905h

Rotations about its three carbon−nitrogen bonds give triethylamine a complex, 3-dimensional potential energy landscape of conformeric structures. Electronic excitation to Rydberg states prepares the molecule in a high-energy, nonequilibrium distribution of such conformers, initiating ultrafast transitions between them. Time-resolved Rydberg electron binding energy spectra, observed using photoionization-photoelectron spectroscopy with ultrashort laser pulses, reveal these time-evolving structures. The time-dependent structural fingerprint spectra are assigned with the aid of a computational analysis of the potential energy landscape. Upon 209 nm electronic excitation to the 3p Rydberg state, triethylamine decays to 3s with a 200 fs time constant. The initially prepared conformer reacts to a mixture of structures with a time constant of 232 fs and settles into a final geometry distribution on a further subpicosecond time scale. The binding energy of the Rydberg electron is found to be an important determinant of the conformeric energy landscape.