Tom Varberg, MacAlester College
March 26, 2004, 3:00
Far-infrared Spectroscopy of Transient Species: Interrogating Small Molecules with Long Wavelengths
It has traditionally been challenging to undertake high-resolution molecular spectroscopy in the far-infrared region, due to a lack of tunable sources of radiation. Laser magnetic resonance spectroscopy is a sensitive technique, but it is limited to paramagnetic species. In this talk, I will describe the technique of tunable far-infrared (TuFIR) spectroscopy, in which the radiation from two carbon dioxide lasers is mixed together on a diode, generating light with a frequency equal to the difference of the two laser frequencies. TuFIR spectroscopy is not very sensitive, but its accuracy is very high (ca. 1 part in 100 million). We have measured pure rotational spectra of several species, including CO, OH, NO, ZnH and CdH. These results are of interests to atmospheric scientists and radioastronomers as well as to spectroscopists.