Spin flip Raman laser

SPIN FLIP RAMAN LASER OPTO-ACOUSTIC SPECTROMETER... 

Radiation from infrared spectrometer source. SFRL Spin flip Raman laser. 

A photoacoustic cell of novel design was described by Patel and Kerl This cell consists of a rectangular waveguide with six electret miniature microphones. For excitation of NO a spin-flip Raman laser was used with 0,1 W power at 5,3 pm. With this apparatus a NO concentration of 1,0 10 molecules/cm could be detected. This corresponds to a measurable absorption coefficient of 10 ° cm" . A similar sensitivity may also be obtainable with Nodov s H-type cell (see Fig. 7 b)... 

We have already discussed the use of electric field modulation as a means of providing the selective detection of those molecular absorption lines having the strongest Stark effects, using tunable lasers as sources ( 2.4). As in microwave spectroscopy, where field modulation is routine, magnetic fields may also be used for this purpose, as was demonstrated by Urban and Herrmann (1978). The spectrum of NO was recorded with extremely high sensitivity using Zeeman modulation with a spin-flip Raman tunable infrared laser. 

The sensitivity of this intracavity technique (Sect. 1.2.3) can even be enhanced by modulating the magnetic field, which yields the first derivative of the spectrum (Sect. 1.2.2). When a tunable laser is used it can be tuned to the center vo of a molecular line at zero field = 0. If the magnetic field is now modulated around zero, the phase of the zero-field LMR resonances for AM = +1 transitions is opposite to that for AM = — 1 transitions. The advantages of this zero-field LMR spectroscopy have been proved for the NO molecule by Urban et al. [143] using a spin-flip Raman laser. 

In paramagnetic molecules Raman transitions between different fine-structure components (spin-flip Raman transitions) can occur [299]. If the molecules are placed in a longitudinal magnetic field parallel to the laser beam, the Raman light is circularly polarized and is measured as light for AM = -hi and as for AM = — 1 transitions. 

W. Urban, W. Herrmann, Zeeman modulation spectroscopy with spin-flip Raman laser. Appl. Phys. 17, 325 (1978)... 

FIGURE 22 (a) Level diagram for a spin-flip Raman laser, (b) Typical tuning curve for an InSb spin-flip Raman laser pumped by a CO2 laser at 10.6 ixm. [Part (b) reproduced from Patel, C. K. N., and Shaw, E. D. (1974). Phys. Rev. B 3,1279.]... 

S.D. Smith, R.B. Dennis, R.G. Harrison The spin-flip Raman laser. Prog. Quant. Electr. 5, 205 (1977)... 

Many of the most widely used tunable coherent infrared sources use various semiconductor materials, either directly as the active laser medium (semiconductor lasers) or as the nonlinear mixing device (spin-flip Raman laser, frequency-difference generation). 

S.D. Smith High resolution Infrared Spectroscopy the spin-flip Raman Laser, in Very High Resolution Spectroscopy ed. by R.A. Smith (Academic, New York 1976)... 

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