“…Numerous improvements can almost certainly be made in terms of optimizing the sample and timing conditions and these are currently being explored. Additional spectral measurements of 13 C isotopologues and Stark effect measurements were carried out in this study using a standard Balle-Flygare type resonant cavity instrument [4,12] although initial assignments of all spectra, including those of the 13 C species (observed in natural abundance), were made with the CP-FTMW spectrometer. Stark effect measurements were carried out by application of voltages up to ±5 kV to a pair of steel mesh plates placed 31 cm apart in the resonant cavity instrument's vacuum chamber, straddling the molecular expansion; electric field calibration was achieved by measurement of the J = 1 0 transition of OCS and assuming a dipole moment of 0.71519(3) D [13].…”