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Updated: May 25, 2025

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Anharmonicity and vibrational Stark fields in phosphinic acid dimers
Manjusha Boda1, Arzoo1, G Naresh Patwari1
1Department of Chemistry, Indian Institute of Technology Bombay, Mumbai 400076, India. naresh@chem.iitb.ac.in.
Phosphinic acid forms stable cyclic dimers through hydrogen bonding, stronger than carboxylic acids. This enhanced stability is linked to electric field effects on OH groups and significant anharmonicity.
Area of Science:
- Chemistry
- Physical Chemistry
- Spectroscopy
Background:
- Phosphinic acid exhibits unique cyclic dimer formation via intermolecular hydrogen bonding.
- These dimers show exceptional stability and higher dimerization enthalpies compared to analogous carboxylic acid dimers.
- Hydrogen bond strength in these dimers can be quantified by evaluating electric fields.
Purpose of the Study:
- To investigate the strength of hydrogen bonding in phosphinic acid dimers.
- To compare the hydrogen bonding characteristics of phosphinic acid dimers with carboxylic acid dimers.
- To explore the relationship between electric fields and vibrational frequency shifts.
Main Methods:
- Evaluation of electric fields along the hydrogen-bonded OH donor groups.
- Analysis of OH stretch vibrational frequency shifts.
- Measurement of Stark tuning rates for primary and secondary substitution effects.
- Comparison of harmonic and anharmonic O-D frequency shifts.
Main Results:
- A linear correlation was observed between OH stretch vibrational frequency and electric field.
- Phosphinic acid dimers exhibited higher Stark tuning rates (45.6 and 11.8 cm-1(MV cm-1)-1) than carboxylic acid dimers (21.9 and 5.7 cm-1(MV cm-1)-1).
- Anharmonic O-D frequency shifts showed significantly higher Stark tuning rates (40-50% increase) compared to harmonic shifts.
Conclusions:
- Phosphinic acid dimers possess stronger hydrogen bonding interactions than carboxylic acid dimers.
- Electric field evaluation is an effective method for studying hydrogen bond strength in these systems.
- The results indicate significant anharmonicity in the O-H/O-D oscillators of phosphinic acid dimers.
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