Fourier transform microwave spectrum

Only the most stable confomer gauche) was observed in the pulsed molecular beam Fourier transform microwave spectrum. 

Kiran B, Li X, Zhai H-J et al (2004) [SiAiti] aurosdane. Angew Chem Int Ed 43 2125-2129 Pulliam RL, Sun M, Flory MA, Ziurys LM (2009) The sub-miUimeter and Fourier transform microwave spectrum of HZnCl. J Mol Spectr 257 128-132... 

Fig.la shows the first 200ps of the fs DFWM spectrum of HCOOH vapor at room temperature. A complete fitting of the spectrum delivers values of rotational and CD constants and information on the diagonal elements of the PT for HCOOH. The rotational and CD constants are in good agreement with reference values from a Fourier-Transform microwave experiment. [7] The experimental spectrum is fitted very well by the simulation (Fig. 2b), except for the region 120-130ps (marked in Fig. 1). The spectral features in this region originate from the formic acid dimer (HCOOHh-...

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. 

The ground-state rotational spectrum of the triply H-bonded DME dimer with three C-H- - -O-C blue-shifting H-bonds has been studied by molecular beam Fourier transform microwave and free jet millimeter wave absorption spectroscopies in Refs. [108,109a] Av xp(C-H) = 13-21 cm-, ... 

A microwave pulse from a tunable oscillator is injected into the cavity by an antenna, and creates a coherent superposition of rotational states. In the absence of collisions, this superposition emits a free-induction decay signal, which is detected with an antenna-coupled microwave mixer similar to those used in molecular astrophysics. The data are collected in the time domain and Fourier transformed to yield the spectrum whose bandwidth is determined by the quality factor of the cavity. Hence, such instruments are called Fourier transform microwave (FTMW) spectrometers (or Flygare-Balle spectrometers, after the inventors). FTMW instruments are extraordinarily sensitive, and can be used to examine a wide range of stable molecules as well as highly transient or reactive species such as hydrogen-bonded or refractory clusters [29, 30]. 

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. ... 

Similar to 2DR, ribose (C5H5O5) is one of the most important monosaccharides since it constitutes a subunit of the backbone of RNA. NMR studies have shown that ribose in solution is a mixture of a- and p-pyranose and a- and p-furanose forms, the p-pyranose form being predominant. The recently settled crystal structures have shown that the a- and P-pyranose forms are present in the solid phase [239-243]. The structure in the gas phase has been experimentally investigated using a laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MBFTMW) technique [62]. The high resolution rotational spectrum has provided structural information on a total of six rotamers of ribose, three belonging to the a-pyranose forms and other three to the P-pyranose forms. Recently, D-ribose (m.p. 95°C) has been submitted to a laser ablation broadband (CP-FTMW) spectroscopic study and eight conformers (two new a-pyranose forms) have been identified. A broadband section of the spectra is shown in Fig. 35 and the detected conformers depicted in Fig. 36. 

From microwave data for the ground state and from a rotational analysis of a Fourier transform UV spectrum for the excited state. 

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. 

FIGURE 9.3 Spectra of the mixture of canthaxanthin (2mM) and A1C13 (2mM) in CH2C12 measured at 60 K at the field B0=3349G and microwave frequency 9.3757 GHz (a) superimposed plot of a set of three-pulse ESEEM spectra as the modulus Fourier transform and (b) HYSCORE spectrum measured with a x=152ns. (From Konovalova, T.A., J. Phys. Chem. B, 105, 8361, 2001. With permission.)... 

ESEEM is a pulsed EPR technique which is complementary to both conventional EPR and ENDOR spectroscopy(74.75). In the ESEEM experiment, one selects a field (effective g value) in the EPR spectrum and through a sequence of microwave pulses generates a spin echo whose intensity is monitored as a function of the delay time between the pulses. This resulting echo envelope decay pattern is amplitude modulated due to the magnetic interaction of nuclear spins that are coupled to the electron spin. Cosine Fourier transformation of this envelope yields an ENDOR-like spectrum from which nuclear hyperfine and quadrupole splittings can be determined. 

For radiofrequency and microwave radiation there are detectors which can respond sufficiently quickly to the low frequencies (<100 GHz) involved and record the time domain spectrum directly. For infrared, visible and ultraviolet radiation the frequencies involved are so high (>600 GHz) that this is no longer possible. Instead, an interferometer is used and the spectrum is recorded in the length domain rather than the frequency domain. Because the technique has been used mostly in the far-, mid- and near-infrared regions of the spectrum the instrument used is usually called a Fourier transform infrared (FTIR) spectrometer although it can be modified to operate in the visible and ultraviolet regions. 

Transverse relaxation is caused by the distribution and fluctuation of the resonance frequency of the A spins. The distribution-induced relaxation is called free induction decay. The free induction decay curve is the Fourier transform of the spectral shape of the A spins. This spectral shape depends on the intensity and the pulse width of the incident microwave, when the total width of ESR spectrum is large as is the case for radical species in solids. Therefore, the analysis of the free induction decay curve gives no information on the nature of radical species in solids unless the pulse width is narrow enough to cover the entire ESR spectrum. 

Fourier transform techniques are used throughout the whole spectroscopic region, particularly in the infrared and visible. As we pass from the microwave region to the far-infrared, Fourier transform methods are still used, but based now on interferometry rather than pulsed methods. Perhaps this region of the spectrum will, in... 

Figure 1 Two-pulse or primary ESEEM data collected for the type-1 Cu(II) site of the Fet3p enzyme. Figure 1(a) shows the time domain data recorded under the following conditions microwave frequency, 9.6883 GHz field strength, 337.0 mT pulse power, 250 W 90° pulse length, 16 ns full width at half maximum (FWHM) sample temperature, 10 K. Figure 1(b) shows the ESEEM spectrum derived from the data of Figure 1(a) by subtraction of a biexponential decay function, application of a Hamming window function, and Fast Fourier Transformation (FFT). The absolute value spectrum is displayed...

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