Lowering type doubling

The V-type double-resonance method of Fig. 5.15a (named after its V-shaped appearance in the level diagram) may be regarded as the inversion of laser-induced fluorescence (Fig. 5.16). With the LIF technique one excited level 2) is selectively populated. The resulting fluorescence spectrum corresponds to all allowed optical transitions from this level into the lower levels m). The analysis of the LIF spectrum mainly yields information on the lower state. With V-type OODR, on the other hand, a single lower level /) is selectively depleted. The OODR transitions, monitored through the difference in the absorption of the probe wave with and without the pump, start from the lower level jl) and end in all upper levels m), which can be reached by probe transitions from 11). They give mainly information about these upper levels. 

If it was a DPDT type (double pole, double throw), then there would be two switches hooked together mechanically, so two movable parts would simultaneously make contact with two upper terminals, or else with two lower terminals. Thus there would be 6 terminals altogether. At any rate, we will use no real switch at all, just a loose clip lead. 

The lower J transitions of the fundamental vibration-rotation spectra of NH" and NH", both in the electronic ground state X ITj, show well-resolved A-type doubling the following constants p and q (in cm" ) for the vibrational levels v = 0 and 1 were derived ... 

The very high quality of ROA spectra makes it possible even to obtain difference ROA spectra of substances at two different temperatures. By this method the premelting of poly(rA)-poly(rU) was monitored. The compound, which has an A-type double helical structure, shows qualitatively the same ROA spectrum at both 20 and 45°C, while the intensities of the bands are lowered. From the fact that the difference spectrum is similar to the ROA spectra at both temperatures, it is concluded that the same average structure is maintained throughout all temperatures in the range examined. The investigation demonstrates the usefulness of the new technique to probe the dynamics of nucleic acids in aqueous solution. 

The effective value of B, for the lower components of the doubled levels, can be obtained from the P and R branches by the same method of combination differences used for a type of band and, for the upper components, from the Q branch. From these two quantities and may be calculated. 

This is in contrast to lasers based on mby or neodymium in glass, which operate at much lower pulse-repetition rates. Nd YAG lasers are often operated as frequency-doubled devices so that the output is at 532 nm. These lasers are the most common type of soHd-state laser and have dominated sohd-state laser technology since the early 1970s. Nd YAG lasers having continuous output power up to 1800 W are available, but output powers of a few tens of watts are much more common. 

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