The 4V(OH) Absorption Spectrum of HDO

Area of Science:

• Molecular Spectroscopy
• Quantum Chemistry

Background:

• Understanding molecular energy levels is crucial for various scientific disciplines.
• Highly excited vibrational states provide insights into molecular dynamics and interactions.

Purpose of the Study:

• To record and analyze the absorption spectrum of HDO in a specific infrared region.
• To identify and assign spectral lines to specific transitions and energy levels.
• To investigate potential perturbations and resonances affecting these energy levels.

Main Methods:

• Intracavity Laser Absorption Spectroscopy (ICLAS) was employed to capture the spectrum.
• Spectral lines were assigned to vibrational and rotational quantum numbers.
• Experimental energy levels were fitted using an effective rotational Hamiltonian.

Main Results:

• 437 HDO spectral lines were identified, with 399 assigned to the 4nu(3) overtone transition.
• 129 experimental energy levels were determined, with rotational quantum numbers up to J=16 and Ka=7.
• The (004) vibrational state was found to be nearly isolated, with high accuracy fitting (RMSD=0.012 cm(-1)).
• Evidence of resonance interactions between the (004) and (052) states was observed, leading to weak transitions.

Conclusions:

• The study provides a precise set of experimental energy levels for HDO.
• The findings validate theoretical models and highlight the importance of considering resonance effects in molecular spectroscopy.
• The accuracy of the experimental data is comparable to high-level ab initio predictions.