Tailored molecular samples for precision spectroscopy experiments

Abstract

The resolution of any spectroscopy experiment is ultimately limited by the observation time. The ability to produce slow, yet intense molecular beams significantly increases the attainable observation time and thus the resolution in the spectroscopic experiment. Such slow molecular samples are ideal starting points for novel precision spectroscopy experiments aiming at, for example, determining the time variation of fundamental constants or the effect of parity violation in chiral molecules. We consider the use of decelerated chiral polar molecules to perform very high-resolution rotational spectroscopy aiming at measuring the energy difference of the two enantiomers due to parity violation. Using molecule velocities around 20 m s(-1) and a microwave resonator consisting of 50 cm-reflectors (in diameter) and a reflector distance of up to one meter, spectral resolutions on the order of only a few Hz become feasible using Fourier transform microwave spectroscopy. This should be sufficient to resolve the parity-violation effect for species containing heavy atoms, such as SOCH3Ph and SeOFI. We also discuss the possibilities to use trapped molecules for high-resolution spectroscopy--and work out their advantages, such as long observation times, and their disadvantages, such as line broadening due to the inhomogeneous trapping fields.

Computation of molecular parity violation using the coupled-cluster linear response approach

“…There have been several proposals to measure parity-violating effects in molecules. However, none of the experimental attempts to confirm the parity-violating effects in molecules have met so far with success [1,17,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The extent of molecular parity violation was initially estimated via theory, and ac- * Corresponding author.…”

Deceleration of supersonic beams using inhomogeneous electric and magnetic fields

“…The time-variation of these constants, which determine the strength of the electromagnetic interaction, and the relative strength of the strong and electroweak interactions, could point toward physics beyond the standard model of particle physics. Such possibilities to exploit precision spectroscopic measurements of small molecules in the search for physics beyond the standard model, are also key to experiments directed toward the search for an electric dipole moment (EDM) of the electron and the measurement of parity-violating energy differences between enantiomeric forms of chiral molecules 7,8 . Early experiments to place an upper limit on the size of the electron EDM were performed on atomic thallium 139 , however more recently the focus has been placed on polar diatomic molecules in which the sensitivity to an electron EDM is enhanced.…”

“…When the terminal Mach number is much larger then one, Equation 8 can be approximated to obtain the terminal temperature,…”

“…The possibility to prepare high-density, velocity controlled, state-selected samples of these species to further improve the measurement precision have been envisaged. Multistage Stark deceleration of chiral molecules is also planned to measure parity violating energy differences using microwave spectroscopy 8 .…”

“…The development of these methods is part of a larger effort, by chemists and physicists, directed toward studying the properties of molecules at temperatures below 1 K. This effort is motivated by the prospects of (i) investigating chemical processes close to the absolute zeropoint temperature 1 where reaction rates and product states are expected to be strongly influenced by resonance and tunneling phenomena 2 , long-range interactions between the reactants, hyperfine effects, nuclear-spin symmetry 3,4 and external fields 5 , (ii) carrying out precision measurements of energy intervals which may permit observation of properties revealing very weak symmetry-violating interactions such as a possible electric dipole moment of the electron 6 , energy differences between two enantiomers of a chiral molecule 7,8 , or even reveal a possible time dependence of fundamental constants 9 , (iii) studying dipole-dipole interactions in molecular gases close to quantum degeneracy 3 or dipole-dipole and many-body interactions in frozen Rydberg gases 10 , with applications in the realization of quantum gates 11,12 , and (iv) studying the properties of ultracold atoms and molecules in the vicinity of cryogenic chip-based devices [13][14][15] . Several review articles which describe this effort in the context of recent or proposed experiments involving cold molecules have been published lately 2,[16][17][18][19][20][21] .…”