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1.
M. V. Muftakhov P. V. Shchukin R. V. Khatymov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(9):1730-1736
Resonant electron attachment by orotic acid molecules (6-COOH-uracil) are studied in the energy range of 0–14 eV via negative ion mass spectrometry. Molecular ions, whose lifetimes relative to electron autodetachment are found to be ~300 μs are recorded in the region of thermal electron energies; they form in the valence state through a vibration-excited resonance mechanism. Unlike unsubstituted uracil, most dissociative processes occur in the low-energy region of <4 eV and are due to carboxylic anions. An absolute cross section of 2.4 × 10?17 cm2 is found for the most intense fragment ions [M–H]– at an output energy of 1.33 eV. The kinetics of decarboxylation is considered for these ions. This could be a model reaction for the last stage of uridine monophosphate biosynthesis. 相似文献
2.
The formation of ions from amino acids (glycine and alanine) and dipeptides (glycylglycine, alanylalanine, and glycylalanine)
under the resonant electron capture conditions was studied by negative ion resonant electron capture mass spectrometry. The
isobaric ions were found, their effective yield curves were experimentally separated, and the elemental composition was determined.
The thermochemical aspect of ion formation was considered, and probable dissociative channels of fragmentation ion formation
and their structures were established on the basis of this aspect. Bond cleavage reactions only and H-shift processes were
revealed. The rearrangements occur presumably through the stage of formation of intramolecular hydrogen bonds. The cross-sections
of formation of ions [M − H]− were measured in the energy range 1.1–1.3 eV. The metastable decay channels of ions [M − H]− and [M − COOH]− were found in the energy range 4.5–7.5 eV for dipeptides, which enabled establishing the genetic relationship between the
parental and daughter ions and revealing hidden fragmentation pathways. 相似文献
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Rearrangement processes with the successive splitting out of HF and CO2 molecules, the contribution of which to the scheme of the fragmentation of the negative molecular ions reaches 99%, are realized in the resonance capture of thermal electrons by molecules of organofluorine compounds (derivatives of di- and tetrafluorocinnamic acids and 1,4-diaryltetrafluorobutadiene).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1547–1549, July, 1990. 相似文献
6.
The dynamics of underground water, hydraulically connected with rivers, is investigated during the passage of floods in the rivers. For two-dimensional filtration fluxes bounded by channels with vertical banks on both sides this problem was investigated in [1–3]; for semibounded fluxes it was investigated in [4–8]. Below this problem is investigated for a symmetrical two-dimensional underground flux bounded on both sides by reservoirs with inclined banks. 相似文献
7.
EP Sheretov VS Gurov MV Dubkov OV Korneeva 《Rapid communications in mass spectrometry : RCM》1999,13(16):1699-1702
In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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9.
Phenol, chlorobenzene and chlorophenol isomers: resonant states and dissociative electron attachment
Khatymov RV Muftakhov MV Mazunov VA 《Rapid communications in mass spectrometry : RCM》2003,17(20):2327-2336
This paper reports a study of resonant dissociative electron attachment (DEA) to the phenol, chlorobenzene, p-, m-, and o-chlorophenol molecules. On the basis of spectroscopic and thermochemical approaches the resonant states of the molecular negative ions (NIs) and the structures of some dissociative decay products are assigned. In the electron energy range up to 3 eV, DEA processes are determined by the two 2[pi*]-shape resonances resulting mainly in formation of [M-H]- and/or Cl- ions. At higher electron energies the energy correlation between peaks in the negative ion effective yield curves and bands of UV spectra allowed identification of the core-excited resonances. The peculiarities of Cl- ion formation and the vibrational fine structure on the effective yield curves of the [M-H]- ions are discussed. The mass spectrometric procedures for measurement of relative cross sections for NI formation are described. 相似文献
10.
The study of resonant electron capture by nitrobenzene molecules showed that some fragmentary negative ions are unstable toward
electron autodetachment. The measured appearance energy of the neutral component of an [M — H]− ion beam does not agree with the energetics of direct dissociation in a molecular ion. The estimation calculations show that
the low appearance energy of [M — H]0 neutral components is caused by isomerization of a molecular ion of nitrobenzene to the 2-nitrobenzene structure followed
by the formation of a phenoxide ion in the autodetachment state.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 367–370, February, 2006. 相似文献