Internal rotation about carbon-carbon bonds allows $N$,$N$-dimethyl-2-butanamine (DM2BA) and $N$,$N$-dimethyl-3-hexanamine (DM3HA) to assume multiple conformeric structures. We explore the equilibrium composition and dynamics between such conformeric structures using Rydberg fingerprint spectroscopy. Time constants for conformeric interconversion of DM2BA (at 1.79 eV of internal energy) are 19 and 66 ps, and for DM3HA (1.78 eV) 23 and 41 ps. For the first time, a time-resolved and quantitative view of conformational dynamics of flexible hydrocarbon molecules at high temperatures is revealed.

• Received 8 January 2007

DOI:https://doi.org/10.1103/PhysRevLett.98.253004