Chirped-pulse fourier transform microwave

CHIRPED-PULSE FOURIER TRANSFORM MICROWAVE SPECTROSCOPY A NEW TECHNIQUE FOR RAPID IDENTIFICATION OF CHEMICAL... 

Chirped-Pulse Fourier Transform Microwave Spectroscopy 291... 

Figure 1 Diagram of the chirped-pulse, Fourier transform microwave spectrometer showing the generation of the the linear frequency sweep which is bandwidth multiplied and amplified. The inset shows the pulse in both time and frequency space. The pulse is broadcast into the chamber through a double-ridge microwave horn and the free induction decay (FID) is collected with another microwave horn. The FID is downconverted to the 0.5 - 11.5 GFIz range before being recorded by the oscilloscope.

G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, B. H. Pate, The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy, J. Mol. Spec. In Press, available online. 

A schematic block diagram of the newly designed chirped-pulse Fourier transform microwave spectrometer CP-FTMW, combined with a ps-pulsed laser ablation system, is given in Fig. 3. The spectrometer, which uses the basic operation of the CP-FTMW instrument [18], is described elsewhere [63], with only the relevant details to this experiment being described here. It operates in the 6.0-18 GHz region. The solid sample, prepared as usual as a rod shape, was placed in a laser ablation nozzle, similar to that previously described [61] (1 in Fig. 3) and vaporized using the second (532 nm) or third (355 nm) harmonics of a ps Nd Y AG laser (i.e. Ekspla, 20 ps, 15 mJ/pulse) (2 in Fig. 3). A motor controller (3 in Fig. 3) allows a DC motor (Oriel Motor Mike 18074) (4 in Fig. 3) to rotate and translate the rod up and down along the injection system to achieve the maximum exploitation of the... 

Fig. 3 Schematics of a laser ablation chirped-pulse Fourier transform microwave spectrometer.

The future perspectives of this research area depend heavily on the application of CP-FTMW spectrometers, which have changed the scope of rotational spectroscopy in recent years. Chirped-pulse Fourier-transform microwave spectroscopy, combined with laser ablation, opens a new era in the investigation of isolated biomolecules, as can be shown by its application to carbohydrates as discussed in this chapter. The broad frequency and large dynamic range make it possible to extend the range of detectable conformers to less stable forms and to access structural determinations in molecular systems of increasingly larger sizes from measurements of heavy atom ( C, 0) isotopes detected in natural abun-... 

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