Slow photoelectron velocity-map imaging of cold and

Area of Science:

• Physical Chemistry
• Spectroscopy
• Molecular Physics

Background:

• Carbon clusters are fundamental building blocks in various chemical and physical processes.
• Understanding the vibronic structure and electronic properties of carbon clusters is crucial for their applications.
• Previous studies lacked high-resolution data on the vibrational modes and electron affinities of C7 and C9 clusters.

Purpose of the Study:

• To present high-resolution anion photoelectron spectra of cryogenically cooled C7- and C9- clusters.
• To elucidate the vibronic structure of neutral C7 and C9 clusters.
• To accurately determine vibrational frequencies and electron affinities for C7 and C9.

Main Methods:

• Slow photoelectron velocity-map imaging technique was employed.
• Cryogenic cooling of C7- and C9- cluster anions.
• Analysis of spectral features, including vibrational frequencies, spin-orbit splitting, and Franck-Condon forbidden transitions.

Main Results:

• Accurate electron affinities were determined: 3.3517(4) eV for C7 and 3.6766(14) eV for C9.
• Vibrational frequencies for several stretching and bending modes of neutral C7 and C9 were assigned.
• Observation and assignment of Franck-Condon forbidden transitions attributed to Herzberg-Teller and vibronic coupling.

Conclusions:

• The study provides unprecedented insight into the vibronic structure of neutral C7 and C9.
• Spin-orbit splitting in C7- and Franck-Condon forbidden transitions in both clusters were characterized.
• Photodetachment cross sections suggest delocalized molecular orbitals with increasing nodal structure in larger carbon chains.