Fourier transform microwave spectroscopy of the SiCl+ ion

Abstract Fourier transform microwave spectra for the J  = 1  ←  0 and 2  ←  1 rotational transitions of the SiCl + ion were observed for two isotopologues ( 35 Cl and 37 Cl) in the ground and the first excited vibrational states of the ground 1 Σ + electronic state. Thanks to the high resolution of the FTMW spectrometer, hyperfine structures due to the quadrupole moment of the chlorine nucleus and the nuclear spin-rotation interaction were fully resolved. The observed FTMW spectra were combined with previously reported MMW and diode laser spectra in an analysis to determine the mass-independent Dunham coefficients U k , l as well as a mass scaling parameter Δ 01 Cl = - 0.856 ( 30 ) . The equilibrium bond length of SiCl + determined is r e = 1.9439729 ( 10 )  A and the nuclear quadrupole coupling constant of Si 35 Cl + is eQq e = - 11.8788 ( 23 )  MHz.