Survey of the high resolution infrared spectrum of methane (12CH4 and 13CH4): Partial vibrational assignment extended towards 12 000 cm−1

We have recorded the complete infrared spectrum of methane 12CH4 and its second most abundant isotopomer 13CH4 extending from the fundamental range starting at 1000 cm−1 up to the overtone region near 12 000 cm−1 in the near infrared at the limit towards the visible range, at temperatures of about 80 K and also at 298 K with Doppler limited resolution in the gas phase by means of interferometric Fourier transform spectroscopy using the Bruker IFS 125 HR prototype (ZP 2001) of the ETH Zurich laboratory. This provides the so far most complete data set on methane spectra in this range at high resolution. In the present work we report in particular those results, where the partial rovibrational analysis allows for the direct assignment of pure (J = 0) vibrational levels including high excitation. These results substantially extend the accurate knowledge of vibrational band centers to higher energies and provide a benchmark for both the comparison with theoretical results on the one hand and atmospheric spectr...