C6- electronic relaxation dynamics probed via time-resolved photoelectron imaging

Area of Science:

• Physical Chemistry
• Chemical Physics
• Spectroscopy

Background:

• Understanding the electronic relaxation dynamics of molecular anions is crucial for chemical reaction mechanisms.
• Carbon cluster anions are relevant in astrochemistry and materials science.

Purpose of the Study:

• To investigate the electronic relaxation dynamics of C6(-) following specific electronic excitations.
• To elucidate the differing relaxation pathways from the C (2Pi(g)) and 2 (2Pi(g)) states.

Main Methods:

• Time-resolved photoelectron imaging (TRPI) was employed.
• Excitation was performed at 607 nm and 498 nm, targeting specific transitions.
• Analysis of photodetachment energy distributions provided insights into relaxation dynamics.

Main Results:

• The C (2Pi(g)) state relaxes on a timescale of ~620 fs, involving direct decay and indirect decay through the A (2Sigma(g)+) state (~2300 fs).
• The 2 (2Pi(g)) state shows much faster relaxation (<100 fs) with transient populations in A (2Sigma(g)+), B (2Sigma(u)+), and C (2Pi(g)) states.
• The optically inaccessible B (2Sigma(u)+) state was experimentally observed with an electronic term value of 1.41±0.05 eV.

Conclusions:

• Different electronic excitations lead to distinct relaxation pathways in C6(-).
• TRPI is a powerful technique for probing ultrafast dynamics and characterizing electronic states in molecular anions.
• The study provides a detailed understanding of the excited-state dynamics of C6(-) relevant to its chemical behavior.