Microwave Fourier Transform Spectroscopy of Rovibrational Transitions in the ν 2 /ν 4 Dyads of Methane- 12 C and - 13 C

The ν2/ν4 dyad-dyad spectra of 12CH4 and 13CH4 molecules in the (8÷20) GHz region have been predicted including line strengths. All transitions with γmax > 810-12 cm-1 have been observed directly using a MWFT spectrometer: six F-type transitions for 12CH4 and nine for 13CH4.