Molecular beam, Fourier-transform

A detailed experimental investigation of the THP-HzO complex (with molecular beam Fourier transform (FT) microwave spectroscopy, free-jet millimeter-wave spectroscopy, and ab inito calculations) revealed that the lowest energy species has the water in an axial position. <1998CEJ1974>. Similar studies into the TFIP-FICl complex allowed both the axial and equatorial hydrogen-bond complexes to be characterized it was not possible to unequivocally determine which of the two is more stable <1999AGE1772>. 

III Pulsed Molecular Beam, Fourier Transform Microwave Spectroscopy 89... 

The hydrogen-bonded heterodimer THF HCl has been investigated by molecular-beam Fourier transform (FT) microwave spectroscopy as well as by MP2/6-31G calculations (THF = tetrahydrofuran). Its three conformations are interrelated by one inversion movement and two pseudorotation movements . 

In 2008, Alonso and coworkers reported a combined experimental and computational study of the conformations of cysteine. They located 11 low lying conformers at MP4/6-311-i i-G(d,p)//MP2/6-311-l-l-G(d,p), and the five lowest energy structures are shown in Table 3.15. Using laser ablation molecular beam Fourier transform microwave spectroscopy, they identified six conformers present in the gas phase. Comparing the computed rotational constants and nuclear quadrupole coupling tensor components with the experiment, they were able to decidedly match up all six experimental conformers with computed structures. Of the five low energy conformers listed in Table 3.15, four of them were identified in the experiment. 

Alonso et al. examined the glycine-one water complex using laser ablation molecular beam Fourier-transform microwave spectroscopy. By comparison of the observed rotational parameters and those predicted from an MP2/6-311+G(d,p) optimization, they concluded that the only observed isomer is that formed of the neutral isomer and water, 44a. Balabin examined the glycine-one water complex using IR spectroscopy. While he too found 44a, he was able to detect a small amount of 44b and 44c. An interesting side note is that anharmonic corrections were necessary in order to match up the computed (MP2) frequencies with the experimental values. These experiments indicate that more than one water molecule is needed to stabilize the zwitterion tautomer. 

The MW spectrum of the and isotopomers of a thiazole-argon van der Waals complex was measured using molecular beam Fourier transform MW spectrometers <1995JST(352)289>. The vibrational frequency of benzothiazole was validated by ab initio calculation of the harmonic force field <1999SAA2437>. 

R. D. Suenram, J. U. Grabow, A. Zuban, I. Leonov, A portable, pulsed-molecular-beam, Fourier-transform microwave spectrometer designed for chemical analysis. Rev. Sci. Instrum., 70(4), 2127-2135 (1999). 

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-, ... 

In order to obtain a precise structure the rotational spectra of 24 isotopomers were studied by molecular beam Fourier transform microwave spectroscopy. The isotopomers of the ethyrtylbenzene subunit are labelled according to... 

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

Only the most stable eonformer (gauche-anti-gauche") was observed in the pulsed molecular beam Fourier transform microwave spectmm. The eonformer is stabilized by an intramolecular N-H -tc hydrogen-bonding interaction. 

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. 

Lopez JC, Pena MI, Sanz ME, Alonso JL (2007) Probing thymine with laser ablation molecular beam Fourier transform microwave spectroscopy. J Chem Phys 2007 126... 

Laser-Ablation Molecular-Beam Fourier Transform Microwave (LA-MB-FTMW) Spectroscopy... 

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. 

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. 

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