Pulse Fourier Transform Spectroscopy

Using the Stark switching technique with varying pulse delay times in an 

Fourier spectrum of a single pulse, two pulses, and of a regular pulse train, a) Field amplitude as a function of time, b) Spectral profile as monitored e.g., by two-photon spectroscopy (after [11.52]) 

Stark pulse on, but radiates when it is off, the emission is Stark shifted from the laser and four heterodyne beat frequencies are produced at the detector, each beat being due to two transitions M M. The four lines are 170 KHz wide and are spaced at 0.83 MHz [11.50]. The exponential decay of the echo signal with increasing delay time t, which is plotted in Fig.11.31, samples the homogeneous dipole dephasing rate due to elastic and inelastic collisions (see Sect.11.4.1). This technique therefore allows measurement of collision rates separately for different M levels. Since different velocity groups of molecules can be sampled, depending on the Stark shift, information on the velocity dependence of the collision rates can also be obtained (see Chap.12). 

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The Reader It is assumed that the reader understands the fundamental principles of pulse Fourier transform spectroscopy (PFT) and is proficient in using the MS-Windows operating system and Windows based programs. The references at the end of section 1.4 list both introductory and comprehensive texts on the main principles of NMR spectroscopy. Furthermore the reader should be familiar with computer environments, as working on a spectrometer inevitable requires computer management skills. 

C NMR Measurements. The NMR spectra were observed with a Varian XL-100 spectrometer modified for pulse Fourier transform spectroscopy and interfaced with a Nicolet model 1080 computer. The protons were decoupled from the carbon nuclei using a random noise decoupling field. Free induction decays were stored in 8K computer locations using a dwell time of 200 / sec, i.e., a spectral window of 2500 Hz. The pulse width was 23/xsec (for a 90° pulse), and the pulse interval was 3.0 sec. Hexamethyldisiloxane was used as an internal reference (2.0 ppm vs. TMS), and the internal deuterium lock signal was... 

With the increased availability of pulse Fourier-transform spectroscopy,... 

Bowring NJ, Andrews DA, and Baker JG (1992) Novel coherence effects in microwave-microwave double resonance pulse Fourier transform spectroscopy. Journal of Physics B Atomic, Molecular and Optical Physics 25 667-677. 

We discuss first some techniques of generating short laser pulses and then illustrate different applications. Methods for lifetime measurements, the quantum beat technique, pulse Fourier transform spectroscopy, and multiple coherent interactions are some of the recently developed methods which demonstrate the capabilities of pulsed lasers for high time-resolution... 

Coherent Transients and Pulse Fourier Transform Spectroscopy... 

Fourier transform spectroscopy in the radio frequency region has been applied most importantly in pulsed Fourier transform NMR spectroscopy, which is not a subject which... 

Radiofrequency spectroscopy (NMR) was introduced in 1946 [158,159]. The development of the NMR method over the last 30 years has been characterised by evolution in magnet design and cryotechnology, the introduction of computer-based operating systems and pulsed Fourier transform methods, which permit the performance of new types of experiment that control production, acquisition and processing of the experimental data. New pulse sequences, double-resonance techniques and gradient spectroscopy allow different experiments and have opened up the area of multidimensional NMR and NMRI. 

Table 5.16 Main characteristics of high-resolution pulse Fourier-transform 1-NMR spectroscopy...

The introduction of additional techniques such as Pulsed Fourier Transform NMR spectroscopy (PFT-NMR) has considerably increased the sensitivity of the method, allowing many magnetic nuclei which may be in low abundance, including 13C, to be studied. The additional data available from these methods allow information on polymer structure, conformation and relaxation behaviour to be obtained (1.18.20). 

Spectra.—Pulsed Fourier-transform n.m.r. spectroscopy of labelled steroids,... 

I. P. Gerothanassis, Methods of avoiding the effects of acoustic ringing in pulsed Fourier transform nuclear magnetic resonance spectroscopy. Prog. Nud. Magn. Reson. Spectrosc., 1987,19, 267-329. 

In order to identify the spin multiplicity of the tris(carbene), field-swept two-dimensional electron spin transient nutation (2D-ESTN) spectroscopy was used. This technique is based on pulsed fourier transform (FT) EPR spectroscopic methods and is capable of elaborating straightforward information on electronic and environmental strucmres of high-spin species even in amorphous materials, information that conventional CW EPR cannot provide. The nutation spectra unequivocally demonstrated that the observed fine structure spectrum is due to a septet spin state. 

The first measurements of pH-dependences of13C spectra of amino acids were carried out by INDOR spectroscopy [96]. Pulse Fourier transform 13C NMR measurements are less... 

The properties of weakly bonded van der Waals complexes in reactive systems are studied by pulsed Fourier Transform microwave spectroscopy, which is a powerful tool for investigating many complexes. 

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