1B2(1Sigma(u)+) excited state decay dynamics in CS2

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Spectroscopy

Background:

• Carbon disulfide (CS2) is a key molecule for studying photochemistry.
• Understanding predissociation dynamics is crucial for molecular reaction mechanisms.
• Previous studies suggested simple decay models for CS2 excited states.

Purpose of the Study:

• To investigate the time-resolved predissociation dynamics of the (1)B2((1)Sigma(u)+) state of CS2.
• To determine if predissociation follows a single exponential decay.
• To explore the influence of laser polarization on dissociation lifetimes.

Main Methods:

• Time-resolved photoelectron spectroscopy.
• Pump-probe laser experiments at 200 nm.
• Biexponential modeling of decay curves.
• Analysis of polarization-dependent lifetimes.

Main Results:

• Predissociation dynamics are not described by a single exponential decay.
• A rapid decay pathway (tau < 50 fs) and a longer-lived channel (tau ≈ 350–650 fs) were identified.
• The apparent lifetime of the longer channel varied with pump-probe laser polarization.
• Observed lifetimes are a superposition of singlet and triplet state decay pathways.

Conclusions:

• Biexponential decay provides a more accurate model for CS2 predissociation.
• Laser polarization influences the observed dissociation lifetimes.
• The interplay between singlet and triplet states, and their ionization cross-sections, explains the polarization dependence.