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.
The chiral C symmetric molecule 1,2-dithiine (1,2-dithia-3,5-hexadiene, CHS) has been identified as a possible candidate for measuring the parity violating energy difference between enantiomers. We report here the observation and analysis of the low-frequency fundamental ν using highest resolution synchrotron-based interferometric Fourier transform infrared (FTIR) spectroscopy in the terahertz range with a band center of ν = 6.95375559 THz (ν̃ = 231.952319 (10) cm) and two related hot bands, the (ν + ν) ← ν band at ν = 6.97256882 THz (ν̃ = 232.579861 (33) cm) and the 2ν ← ν band at ν = 7.01400434 THz (ν̃ = 233.962001 (14) cm). This success in the difficult analyses of the THz spectrum of a complex chiral molecule of importance for fundamental tests on molecular parity violation is enabled by the ideal setup of an FTIR experiment of currently unique resolution with the very stable and bright synchrotron radiation at the Swiss Light Source (SLS).
We report the first successful high-resolution analyses of the Fourier transform infrared (FTIR) spectrum of trisulfane. A band centered at 861.0292 cm can be assigned unambiguously to the chiral trans conformer by means of ground state combination differences in comparison with known rotational spectra. A second band near 864.698 cm is tentatively assigned to the cis conformer by comparison with theory. The results are discussed in relation to their importance for experimental attempts to measure the parity violating energy difference ΔE between the ground states of enantiomers of chiral molecules.
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