Laser-microwave double resonance

H. Jones, Laser microwave-double-resonance and two-photon spectroscopy. Comments At. Mol. Phys. 8, 51 (1978)... 

W.E. Ernst, S. Kindt, A molecular betim laser-microwave double resonance spectrometer for precise measurements of high temperature molecules. Appl. Phys. B 31,79 (1983)... 

W.E. Ernst, S. Kindt, K.P.R. Nair, and T. Torring, Determination of the ground state dipole moment of CaCl from molecular-beam laser-microwave double resonance measurements, Phys.Rev.A 29 1158... 

Other experiments, carried out recently and based on nonlinear effects, involve laser-microwave double resonance measurements with intense Stark fields on H2CO, spectroscopy on NH3 and NH3 by intracavity... 

Spectroscopy conducted on ions which have been trapped by an appropriate configuration of fields leads to results void of inhomogeneous broadening sources and allows measurements with high spectral resolution. In a recent laser-microwave double resonance experiment conducted on Yb trapped ions, Blatt and co-workers (1983) resolved the ground state hyperfine splitting of the 171 isotope with a Q-factor, i.e., Avlv, of 10 . 

Optical-microwave double resonance (OMDR) can considerably improve the situation and extends the advantages of microwave spectroscopy to excited vibrational or electronic states, because selected levels in these states can be populated by optical pumping. Generally dye lasers or tunable diode lasers are used for optical pumping. However, even fixed frequency lasers can often be used. Many lines of intense infrared lasers (for example, CO2, N2O, CO, HF, and DF lasers) coincide with rotational-vibrational transitions of polyatomic molecules. Even for lines that are only close to molecular transitions the molecular lines may be tuned into resonance by external magnetic or electric fields (Sect. 1.6). The advantages of this OMDR may be summarized as follows ... 

Fig. 5.12 Infrared-microwave double resonance in NHs. The microwave transitions between the inversion doublets can start from the laser-pumped level (signal S) or from levels where the depletion has been transferred by collisions (secondary DR signals S S") [534]...

Major advantages of microwave-optical polarization spectroscopy are narrower linewidths as compared to conventional laser-rf double resonance and smaller intensities required for the laser light field and the micro-waves, so that strongly saturating conditions can be avoided. Therefore, the sensitivity as well as the resolution can be greatly enhanced. 

Clarke and Hofeldt determined the depopulation rates for the individual triplet state spin sublevels of chlorophyll a and chlorophyll b by microwave-modulated fluorescence intensity measurements. The species was dissolved in n-octane at a temperature of 2 K. The solvent n-octane is a low-temperature host matrix which allows high-resolution spectroscopy in the chlorophyll triplet state. Triplet absorption detection of magnetic resonance as well as fluorescence-microwave double resonance techniques were applied. The experimental arrangement was described in Ref. 167. In the case of fluorescence detection, chlorophyll b was irradiated with the 457.9-nm single-mode line of an Ar" laser. Microwave transitions were... 

The band origins of the components and 2v2 of the Fermi diad were determined from an IR-microwave double-resonance investigation using several lines of the CO2 and the N2O lasers =928.067 and 2v2 = 916.040, both 0.001 cm [19]. 

The rotational structure in the region of the Fermi diad v, 2V2 (900 to 955 cm" ) was partly resolved. The comparison with a calculated curve led to the band origins [4]. Seven rotational -vibrational transitions in this range were observed and classified by IR-microwave double resonance using five CO2 and two N2O laser lines [14]. 

Meth. MW MBER Last IRIRDR IRMWDR method of measurement for ft microwave spectroscopy molecular beam electric resonance Laser Stark spectroscopy infrared-infrared double resonance infrared-microwave double resonance... 

Volume n/24 presents the spectroscopic data on diamagnetic and paramagnetic molecules as well as on molecular ions and radicals up to date considering the publications up to and partly including 1997. 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, double resonance and saturation techniques. Some other methods are considered if the accuracy of the derived molecular parameters is comparable to that of microwave spectroscopy owing to a good statistics in the analysis of data, and no microwave data are available. Examples would be Fourier infrared spectroscopy or laser induced fluorescence. 

Problem 10.4. In an optical microwave double resonance experiment the decrease of the population Nj due to excitation into level k) by a CW laser is 20%. The lifetime of the upper level is = 10 s. The collisional refilling rate of level i) is 5 10 s". Compare the magnitude of the microwave signals k) m) between rotational levels... 

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