Rabi-technique

Even at moderate laser powers the optical transition may become saturated (Sect. 2.1) and the lower level i ) can be appreciably depleted. This considerably increases the population difference AA = N ij) — N i ) and thus the absorption of the RF field on the transition ij) i ), which is proportional to AN. In the conventional Rabi technique the population N(E) follows a Boltzmann distribution, and for AE < kT the difference AN becomes very small. 

These advantages allow the extension of the laser Rabi technique to a large variety of different problems [526], which shall be illustrated by three examples ... 

Example 5.9 An impressive example of the OMDR version of the Rabi technique is the measurement of the hyperfine splittings in the electronic ground state of CaCl [543], where linewidths as small as 15 kHz could be achieved for the OMDR signals. They were only limited by the transit time of... 

The Rabi technique of radio frequency or microwave spectroscopy in atomic or molecular beams [10.14-10.17] has made outstanding contributions to the accurate determination of ground state parameters, such as the hfs splittings in atoms and molecules, small Coriolis splitting in rotating and vibrating molecules, or the narrow rotational structures of weakly bound van der Waals complexes [10.18]. Its basic principle is illustrated in Fig. 10.9. A collimated beam of molecules with a permanent dipole moment is deflected in a static... 

The small magnetic hfs in the E state of a homonuclear diatomic molecule is caused by the interaction of the nuclear spins / with the weak magnetic field produced by the rotation of the molecule. For the Nai molecular ground state the hyperfine splittings are smaller than the natural linewidth of the optical transitions. They could nevertheless be measured by the laser version of the Rabi technique [10.21]. A polarized argon laser beam at A, = 476.5 nm crosses the sodium beam and excites the Na2 molecules on the transition X = 0, 7" = 28) n (v = 3,7 = 27). The hfs... 

The combination of electron-impact excitation with the laser version of the Rabi technique allows measurements of hfs splittings in higher excited states. Penselin and coworkers [10.23,24] have developed the atomic beam RF resonance apparatus shown in Fig. 10.10. Metals with a high condensa-... 

While the fine structure transitions are inherently magnetic dipole transitions, it is in fact easier to take advantage of the large A = 1 electric dipole matrix elements and drive the transitions by the electric resonance technique, commonly used to study transitions in polar molecules.37 In the presence of a small static field of 1 V/cm in the z direction the Na ndy fine structure states acquire a small amount of nf character, and it is possible to drive electric dipole transitions between them at a Rabi frequency of 1 MHz with an additional rf field of 1 V/cm. 

FIGURE 23 Illustration of the STIRAP technique used for coherent population transfer. Shown are the time evolution of (a) the Rabi frequencies of the pump and Stokes lasers, (b) the mixing angle, (c) the dressed-state eigenvalues, and (d) the populations of the initial and final levels. [Reproduced with permission from Bergmann, K., Theuer, H., and Shore, B. W. (1998) Rev. Mod. Phys. 70, 1003.]... 

To summarize this section, we have presented a new technique for studying radiation absorption in the molecular system Vi5 constituting a first step towards the observation of Rabi oscillations in molecular nanomagnets. The main results are the observation of relatively narrow resonant absorption lines that are dominated by hyperfine interaction. In order to observe Rabi oscillations in a magnetic system, an important requirement is a large AC field amplitude. 

We have omitted from Table XII.5 the large body of the literature on the reactions of the alkali metal atoms with halogens and alkali halides obtained by the diffusion flame technique of Polanyi. The reason is that the data from these reactions cannot be used to obtain absolute rate constants or activation energies directly, but instead, assumptions must be introduced concerning the kinetic cross reactions and diffusion constants. Reed and Rabi no witch have given an excellent analysis of some of the more troublesome features of the technique. It is of interest, however,... 

Despite attempts to use curare for a variety of diseases including epilepsy, chorea and rabies, the lack of pure and accurately standardised preparations, as well as the absence of convenient techniques of mechanical ventilation if overdose occurred, prevented it from gaining any firm place in medical practice until 1942, when these difficulties were removed. 

Bent NNO-HF was first detected by Klemperer and co-workers using a Rabi-type molecular beam electric resonance spectrometer [161]. They obtained rotational constants and projections of the dipole moment on the a-and fi-axes of the complex. It was found that the N2O axis makes an angle of 47° with the separation between the N2O and HFCMs, which was found to be 3.5 A. Hydrogen appears to be near the O atom with an NOH angle of 116°. Subsequent molecular beam experiments by Dayton and Miller also detected the bent isomer, but in this work an infrared laser was used to excite the HF chromophore [162]. Matrix isolation techniques, in... 

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