Abstract
A comprehensive study of the mass sensitivity of the vibration-rotation-inversion transitions of (NH3)-N-14, (NH3)-N-15, (ND3)-N-14 and (ND3)-N-15 is carried out variationally using the trove approach. Variational calculations are robust and accurate, offering a new way to compute sensitivity coefficients.
Particular attention is paid to the Delta k = +/- 3 transitions between the accidentally coinciding rotation-inversion energy levels of the nu(2) = 0(+), 0(-), 1(+) and 1(-) states, and the inversion transitions in the nu(4) = 1 state affected by the 'giant' l-type doubling effect. These transitions exhibit highly anomalous sensitivities, thus appearing as promising probes of a possible cosmological variation of the proton-to-electron mass ratio mu.
Moreover, a simultaneous comparison of the calculated sensitivities reveals a sizeable isotopic dependence which could aid an exclusive ammonia detection.