Photodissociation dynamics of CF₃CHO: C-C bond cleavage

Area of Science:

• Photochemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Trifluoroacetaldehyde (CF3CHO) is a molecule of interest for understanding photodissociation.
• Its dissociation into CF3 and HCO radicals is relevant to atmospheric chemistry.
• Previous studies have explored its UV absorption spectrum.

Purpose of the Study:

• To elucidate the photodissociation dynamics of CF3CHO.
• To determine the energy barriers and thresholds for dissociation pathways.
• To investigate the role of excited singlet and triplet states in the dissociation process.

Main Methods:

• Velocity-mapped ion imaging was used to study dissociation.
• Laser-induced fluorescence spectroscopy determined the S1 ← S0 transition origin.
• High-level theoretical calculations complemented experimental data.

Main Results:

• Dissociation proceeds via triplet (T1) or ground (S0) electronic states.
• The T1 barrier was determined to be 368.3 ± 2.4 kJ mol−1.
• The S0 dissociation threshold was found to be 335.7 ± 1.8 kJ mol−1.
• The S1 origin was assigned at 28,903 cm−1.

Conclusions:

• The photodissociation mechanism is energy-dependent, involving intersystem crossing and internal conversion.
• Experimental and theoretical methods provide a comprehensive understanding of CF3CHO photodissociation.
• These findings contribute to the understanding of radical formation in atmospheric processes.