Time-resolved dynamics of NO2 in its conical intersection region

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Understanding the photodissociation of nitrogen dioxide (NO2) is crucial for various chemical and atmospheric processes.
• The conical intersection region in NO2's excited states plays a significant role in its ultrafast dissociation pathways.
• Previous studies have explored NO2 photodissociation, but real-time dynamics, especially concerning polarization effects, require further investigation.

Purpose of the Study:

• To experimentally explore the real-time photodissociation dynamics of NO2 in its conical intersection region.
• To investigate the influence of pump-probe laser polarization configurations on the dissociation pathways of NO2.
• To elucidate the role of Rydberg states in the ultrafast dissociation dynamics of NO2.

Main Methods:

• Time-of-flight mass spectrometry was employed to monitor parent (NO2+) and fragment (NO+) ions.
• Femtosecond laser pulses were used for excitation (400.6 nm) and probing (801.6 nm).
• Experiments were conducted using both parallel and perpendicular pump-probe laser polarization configurations.

Main Results:

• Distinct oscillatory signals were observed for NO2+ and NO+ ions under perpendicular laser polarization.
• These oscillations became less distinct or 'blurry' under parallel laser polarization.
• Transient signals indicate that the dissociation mechanism of NO2 from the A(2)B(2) excited state may need reevaluation.

Conclusions:

• The photodissociation dynamics of NO2 are highly sensitive to the relative polarization of pump and probe laser fields.
• The observed transient signals suggest a complex dissociation mechanism involving conical intersections.
• Rydberg states are identified as playing a significant role in the ultrafast dissociation dynamics of NO2.