Infrared/radio-frequency double resonance

Figure 11.47. Magnetic hyperfine and spin-rotation splitting of the v = 17, N= 1 level of HD+. The infrared transitions indicated correspond to the lines observed in figure 11.43. The five radio frequency double resonance transitions observed were all between the G = 0 and 1 levels.

RFIRDR radio frequency infrared double resonance... 

Volume 11/19 brings the spectroscopic data on diamagnetic and paramagnetic molecules as well as on molecular ions up to date considering the publications up to and partly including 1990, in subvolume d up to 1993. The spectroscopic information collected in this volume has been obtained principally from gas phase microwave measurements. In addition, gas phase data have been included derived frOm methods related to microwave spectroscopy by employing a coherent radiation source. These are molecular beam techniques, radio frequency spectroscopy, electron resonance spectroscopy, laser spectroscopy, and double resonance techniques. Some other methods are considered if the accuracy of the derived molecular parameters is comparable to that of microwave spectroscopy and no microwave data are available. Examples would be Fomier infrared spectroscopy or electric deflection methods. 

A radical is defined to be a molecule in an open shell electronic state. It is often, although not necessarily, very reactive and short-lived in a laboratory environment. Several new species have been studied since the publication of the previous supplement, although the number for which microwave transition frequencies have been measured is still quite small. Many of the new observations have been made by radio astronomers who now have access to frequencies up to 350 GHz. Experiments employing double resonance techniques (simultaneous irradiation with microwaves and either infrared or visible radiation) have also made a contribution to the development of the field. The information about linear molecules, in 2, 2, and states, is contained in section 3.2.1. The non-linear radicals, almost all of which are triatomic, are presented in 3.2.2 (Non-Unear triatomic) and 3.2.3 (Non-linear larger molecules). 

---