Precise frequency measurement of pure rotational transitions in the vibrationally excited state of molecule

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Frequencies of pure rotational transitions in the vibrationally excited states of molecules have been measured as precise as ordinary microwave spectroscopy. The obtained frequency data are necessary for examining proposed theories of molecules. A tunable far-infrared spectrometer of Toyama university was used in the study. Precision of rotational frequency data was improved by more than two orders of magnitude in the present study.Firstly, the first excited state of υ2 vibrational mode of HィイD22ィエD2O molecule were investigated. Weak rotational transitions in the vibrationally excited state were successfully observed and measured by our tunable far-infrared spectrometer. Furthermore, a hot sample cell was designed, constructed, and used to observe weaker rotational transitions. Comparing our frequency data with calculated frequencies based on previously reported molecular parameters, it was proved that calculation based on old parameters sometimes brings discrepancies as large as several hundred MHz. A new set of molecular parameters was determined using our data. A high power diode laser system was also desiged and constructed in order to optically pump molecules to highly excited state of vibration.Secondly, rotational. frequency in the vibrationally ground state of HィイD22ィエD2ィイD117ィエD1O, HィイD22ィエD2ィイD118ィエD1O, DィイD22ィエD2O were measured. Together with frequency data in the vibrationally excited state, these data of isotopomers are necessary for checking the validity of newly proposed molecular theories.