A mini-photofragment translational spectrometer with ion velocity map imaging using low voltage acceleration

Area of Science:

• Chemical Physics
• Spectroscopy
• Molecular Dynamics

Background:

• Traditional ion velocity map imaging (VMI) spectrometers require high voltages, leading to complex and bulky apparatus.
• Miniaturization of VMI instruments is desirable for enhanced accessibility and operability.

Purpose of the Study:

• To construct and evaluate a compact, time-sliced ion velocity map imaging photofragment translational spectrometer utilizing low voltage acceleration.
• To demonstrate the advantages of low voltage acceleration in VMI for achieving high resolution in a miniaturized instrument.

Main Methods:

• Developed a mini VMI spectrometer with a short flight path (12 cm) and low acceleration voltage (30-150 V).
• Employed ion trajectory simulations to optimize instrument design and operating parameters.
• Calibrated the spectrometer using photodissociation and multiphoton ionization of O2 at 224.999 nm.
• Tested performance with CF3I dissociation at 277.38 nm to resolve vibrational states and measure anisotropy.

Main Results:

• Achieved a velocity resolution (Δν/ν) of approximately 0.8% for O2 photodissociation, surpassing many high-voltage systems.
• Successfully resolved multiple vibrational states of CF3 following CF3I dissociation.
• Measured the anisotropy parameter for CF3I dissociation.
• Demonstrated the feasibility of miniaturizing VMI instruments without compromising resolution through low voltage acceleration.

Conclusions:

• The developed mini VMI spectrometer with low voltage acceleration is a compact and high-performance instrument.
• Low voltage acceleration offers significant advantages for VMI, enabling miniaturization while maintaining high resolution.
• This approach facilitates detailed studies of molecular photodissociation dynamics.