Vibrational dynamics. Experimental ground-state combination differences of CH₅⁺

Area of Science:

• Molecular spectroscopy
• Quantum chemistry
• Physical chemistry

Background:

• Methane ion (CH5(+)) is a challenging floppy molecule for spectroscopic analysis.
• Previous experimental measurements of CH5(+) spectra were limited.

Purpose of the Study:

• To obtain high-resolution, low-temperature spectra of mass-selected CH5(+).
• To determine the ground state energy levels and assign quantum numbers for CH5(+) nuclear spin isomers.

Main Methods:

• Utilized two action spectroscopy techniques: photoinduced reaction with CO2 and photoinhibition of helium cluster growth.
• Acquired high-resolution spectra of pure CH5(+) samples.

Main Results:

• Achieved very high accuracy in measured line positions.
• Determined a spectrum of combination differences for CH5(+).
• Derived accurate ground state-level schemes for CH5(+) nuclear spin isomers.

Conclusions:

• The study provides a definitive spectroscopic description of CH5(+).
• Enables accurate quantum mechanical analysis of this complex molecular ion.
• Paves the way for further understanding of floppy molecular systems.