Enhanced sensitivity to a possible variation of the proton-to-electron mass ratio in ammonia

Abstract

Numerous accidental near-degeneracies exist between the $2{\nu }_2$ and ${\nu }_4$ rotation-vibration energy levels of ammonia. Transitions between these two states possess significantly enhanced sensitivity to a possible variation of the proton-to-electron mass ratio $\mu$. Using a robust variational approach to determine the mass sensitivity of the energy levels along with accurate experimental values for the energies, sensitivity coefficients have been calculated for over 350 microwave, submillimetre and far infrared transitions up to $J=15$ for ${}^{14}$NH${}_3$. The sensitivities are the largest found in ammonia to date. One particular transition, although extremely weak, has a sensitivity of $T=-16,738$ and illustrates the huge enhancement that can occur between close-lying energy levels. More promising however are a set of previously measured transitions with $T=-32$ to $28$. Given the astrophysical importance of ammonia, the sensitivities presented here confirm that ${}^{14}$NH${}_3$ can be used exclusively to constrain a spatial or temporal variation of $\mu$. Thus, certain systematic errors which affect the ammonia method can be eliminated. For all transitions analyzed we provide frequency data and Einstein A coefficients to guide future laboratory and astronomical observations.

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Cited by in corpus (7)

• Enhanced Sensitivity to Ultralight Bosonic Dark Matter in the Spectra of the Linear Radical SrOH
• The rotation-vibration spectrum of methyl fluoride from first principles
• General variational approach to nuclear-quadrupole coupling in rovibrational spectra of polyatomic molecules
• Diatomic rovibronic transitions as potential probes for proton-to-electron mass ratio across cosmological time
• Simulating electric field interactions with polar molecules using spectroscopic databases
• Hyperfine-resolved rotation-vibration line list of ammonia (NH${}_3$)
• Anomalous phosphine sensitivity coefficients as probes for a possible variation of the proton-to-electron mass ratio