Fourier transform microwave spectrometer

Figure 10.16. Schematic block diagram of a pulsed-nozzle Fourier transform microwave spectrometer [15].

The most important and unique part of a Fourier transform microwave spectrometer is the Fabry Perot cavity. A fairly complete description of the principles has been given by Balle and Flygare [14] and we here summarise the main aspects, with the aid of figure 10.19. We use the cavity built by Balle and Flygare as a typical example. It is formed by two parallel, spherical concave mirrors made from solid aluminium. The mirrors are 36 cm in diameter, have a radius of curvature (R) of 84 cm, and are situated... 

Figure 10.36. Schematic diagram of the laser vapourisation source and pulsed Fourier transform microwave spectrometer developed to study rare earth oxides [88].

Gillies [237], They used the technique of laser ablation to form nozzle beams of the molecules, injected into a Fourier transform microwave spectrometer. In both cases the ground electronic state is 4X, an example of which we met in chapter 9, the excited a state of the CH radical. However in that example the coupling was close to case (b), whereas VO and NbO provide examples of a case (a) 4 XV state. The = 1/2 and 3/2 states are split by second-order spin-orbit coupling the splitting is... 

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.

J. U. Grabow, W. Stahl, H. Dreizler, A multioctave coaxially oriented beam-resonator arrangement Fourier-transform microwave spectrometer. Rev. Sci. Instrum, 67(12), 4072-4084 (1996). 

G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, and B. H. Pate, A Broadband Fourier Transform Microwave Spectrometer Based on Microwave Chirped Pulse Excitation, Rev. Sci. Instrum., In Preparation. 

Figure Bl.4.4. (a) An outline of the Harvard University electric discharge supersonic nozzle/Fourier transform microwave spectrometer, (b) The rotational states of HCj N observed with this apparatus [31],...

From Suenram RG, Grabow J, Zuban A, and Leonov I (1999) A portable pulsed-molecular-beam Fourier-transform microwave spectrometer designed for chemical analysis. Review of Scientific Instruments 70 2127-2135. 

Neutral homoleptic platinum carbonyls remain unknown under normal laboratory conditions. Platinum monocarbonyl, PtCO, has been prepared by laser ablation of Pt in the presence of GO, and its pure rotational spectrum measured between 6,500 and 20,000 M Hz, using a cavity-pulsed jet Fourier transform microwave spectrometer. A Pt-G bond length of 1.760 and a G-O bond length of 1.148 A were measured, and may be rationalized in the conventional terms of cr-donation from and vr-backbonding to the GO. ... 

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.

Balle TJ, Flygare WH (1981) Fabry-Perot cavity pulsed Fourier-transform microwave spectrometer with a pulsed nozzle particle source. Rev Sci Instnun 52 33-45... 

The CW microwave spectrometer just described is a typical frequency-domdim instrument. In the late 1970s it was demonstrated that pulsed /m -domain microwave spectroscopy could be practically performed in analogy to the techniques already well known in other fields such as NMR spectroscopy. Figure 2 depicts a block diagram of a modern version of a pulsed Fourier-transform microwave spectrometer. The particular instrument shown utilizes a Fabry-Perot cavity and a pulsed-gas nozzle, and is especially useful for detecting microwave... 

Figure 2 Block diagram of pulsed Fourier-transform microwave spectrometer. Reproduced with permission of the American Institute of Physics from Harmony MD, Reran KA, Angst DM and Ratzlaff KL (1995). A compact hot-nozzle Fourier transform microwave spectrometer. Review of Scientific Instruments 66 5196-5202. Copyright 1995, American Institute of Physics.

FIGURE 25 The N-quadrupole hyperfine structure of the Oo,o->- 1q,i transition of various isotopic species of HN3. The center frequencies have been aligned for display purposes. The spectra were obtained with a Fourier transform microwave spectrometer. (a) Observed coupling pattern for H N3, (b) calculated coupling pattern for H N3, (c) observed coupling pattern for (d) observed coupling pattern for... 

Lesarri, A., Mata, S., Lopez, J.C., and Alonso, J.L. (2003) A laser-ablation molecular-beam Fourier-transform microwave spectrometer the rotational spectrum of organic solids. Rev. Sd. Instrum., 74 (11), 4799-4804. 

---