13 research outputs found
Bifunctional Hydrogen Bonding of Imidazole with Water Explored by Rotational Spectroscopy and DFT Calculations
Barriers to internal rotation in methylimidazole isomers determined by rotational spectroscopy
A chalcogen-bonded complex (CH<sub>3</sub>)<sub>3</sub>N<sup>...</sup>S=C=O characterised by rotational spectroscopy
A chalcogen-bonded complex H<sub>3</sub>N⋯S=C=S formed by ammonia and carbon disulfide characterised by chirped-pulse, broadband microwave spectroscopy
Microwave Spectra, Molecular Geometries, and Internal Rotation of CH<sub>3</sub> in <em>N</em>-methylimidazole...\ubcH<sub>2</sub>O and 2-methylimidazole...\ubcH<sub>2</sub>O Complexes
Cooperative hydrogen bonding in thiazole⋯(H<sub>2</sub>O)<sub>2</sub> revealed by microwave spectroscopy
Molecular Geometries and Other Properties of H<sub>2</sub>O⋯AgI and H<sub>3</sub>N⋯AgI as Characterised by Rotational Spectroscopy and <em>Ab Initio</em> Calculations
Cooling dynamics of energized naphthalene and azulene radical cations
Naphthalene and azulene are isomeric polycyclic aromatic hydrocarbons (PAHs) and are topical in the context of astrochemistry due to the recent discovery of substituted naphthalenes in the Taurus Molecular Cloud-1 (TMC-1). Here, the thermal- and photo-induced isomerization, dissociation, and radiative cooling dynamics of energized (vibrationally hot) naphthalene (Np+) and azulene (Az+) radical cations, occurring over the microsecond to seconds timescale, are investigated using a cryogenic electrostatic ion storage ring, affording “molecular cloud in a box” conditions. Measurement of the cooling dynamics and kinetic energy release distributions for neutrals formed through dissociation, until several seconds after hot ion formation, are consistent with the establishment of a rapid (sub-microsecond) Np+ ⇌ Az+ quasi-equilibrium. Consequently, dissociation by C2H2-elimination proceeds predominantly through common Az+ decomposition pathways. Simulation of the isomerization, dissociation, recurrent fluorescence, and infrared cooling dynamics using a coupled master equation combined with high-level potential energy surface calculations [CCSD(T)/cc-pVTZ], reproduce the trends in the measurements. The data show that radiative cooling via recurrent fluorescence, predominately through the Np+ D0 ← D2 transition, efficiently quenches dissociation for vibrational energies up to ≈1 eV above dissociation thresholds. Our measurements support the suggestion that small cations, such as naphthalene, may be more abundant in space than previously thought. The strategy presented in this work could be extended to fingerprint the cooling dynamics of other PAH ions for which isomerization is predicted to precede dissociation