IRPD spectroscopy and ensemble measurements: effects of different data acquisition and analysis methods

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Infrared photodissociation (IRPD) spectroscopy is crucial for characterizing hydrated metal cations.
• Comparing different IRPD acquisition and analysis methods is essential for accurate structural determination.
• Blackbody infrared radiative dissociation can complicate IRPD analysis of large clusters.

Purpose of the Study:

• To compare three common IRPD spectroscopy methods using a La(3+)(H(2)O)(36) dataset.
• To introduce and validate a new ensemble IRPD method for analyzing hydrated ion clusters.
• To assess the advantages of using photodissociation rate constants for IRPD intensity measurements.

Main Methods:

• Comparison of first-order photodissociation rate constant, photodissociation yield, and depletion/appearance methods.
• Development and application of a new ensemble IRPD spectroscopy technique.
• Analysis of La(3+)(H(2)O)(36) and La(3+)(H(2)O)(35-37) cluster ensembles.

Main Results:

• The first-order photodissociation rate constant method offers advantages for comparing IRPD intensities with calculated spectra.
• The new ensemble IRPD method provides spectra nearly equivalent to the rate constant method for single ions.
• Ensemble IRPD spectra reveal average cluster structures and improve signal-to-noise ratios without increasing acquisition time.

Conclusions:

• The first-order rate constant method is advantageous for quantitative IRPD analysis.
• The novel ensemble IRPD method is effective for studying the average structures of hydrated ion clusters.
• This work advances the application of IRPD spectroscopy to complex ionic systems.