Abstract
We report high resolution spectroscopic results of 1,2-dithiine-(1,2-dithia-3,5-cyclohexadiene, C4H4S2) in the gigahertz and terahertz spectroscopic ranges and exploratory theoretical calculations of parity violation and tunneling processes in view of a possible experimental determination of the parity violating energy difference ΔpvE in this chiral molecule. Theory predicts that the parity violating energy difference between the enantiomers in their ground state (ΔpvE ≃ 1.1 × 10(-11)(hc) cm(-1)) is in principle measurable as it is much larger than the calculated tunneling splitting for the symmetrical potential ΔE± < 10(-24) (hc) cm(-1). With a planar transition state for stereomutation at about 2500 cm(-1) tunneling splitting becomes appreciable above 2300 cm(-1). This makes levels of well-defined parity accessible to parity selection by the available powerful infrared lasers and thus useful for one of the existing experimental approaches towards molecular parity violation. The new GHz spectroscopy leads to greatly improved ground state rotational parameters for 1,2-dithiine. These are used as starting points for the first successful analyses of high resolution interferometric Fourier transform infrared (FTIR, THz) spectra of the fundamentals ν17 (1308.873 cm(-1) or 39.23903 THz), ν22 (623.094 cm(-1) or 18.67989 THz) and ν3 (1544.900 cm(-1) or 46.314937 THz) for which highly accurate spectroscopic parameters are reported. The results are discussed in relation to current efforts to measure ΔpvE.
Highlights
The experimental proof of principle has been demonstrated for the simple achiral molecule NH3, where the current experimental sensitivity indicates that parity violating energy differences on the order of about 100 aeV or 10À12 cmÀ1 corresponding to about DpvH~ 0 = 10À11 J molÀ1 should be detectable with the existing set-up.[70]
In the present work we show that the chiral molecule 1,2-dithiine is a possible candidate for experiments on DpvE by carrying out in essence steps 1 and 2 of the program listed above
1,2-Dithiine was synthesized according to the scheme in Fig. 6 using a procedure which is a modification of ref. 81, as described here, because the original procedure from ref. 81, which was tried as well, did not give quite satisfactory results in step c
Summary
Recent detailed theoretical simulations have shown the feasibility of such experiments, in principle, for the realistic, simple chiral molecule ClOOCl.[68,69] the experimental proof of principle has been demonstrated for the simple achiral molecule NH3, where the current experimental sensitivity indicates that parity violating energy differences on the order of about 100 aeV or (hc) 10À12 cmÀ1 corresponding to about DpvH~ 0 = 10À11 J molÀ1 should be detectable with the existing set-up.[70] Such values are predicted for chiral molecules with atoms no heavier than sulfur or chlorine[71] which is a great advantage for a future theoretical analysis of experiments with very high accuracy[9,44] in addition to the advantage of providing separate values for individual DpvE Another advantage of the second scheme is that experiments can be carried out on racemic mixtures as well as on separate enantiomers. A preliminary report on the present research has been given in ref. 92–94
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