Фрагментация молекулы глютамина электронным ударом

Using the mass-spectrometric analysis technique, formation of the ionic products of the single and dissociative ionization of the glutamine molecule (C5H10N2O3) at its interaction with the low (70 eV) and high (11.5 MeV) energy electrons has been studied. The experimental mass-spectra of the above molecule measured at different irradiation doses (5, 10 and 20 kGy) and the near-threshold areas of the ionic fragment yield functions have been analyzed, the absolute ion fragment appearance energies have been found. The three-electrode electron gun and the electron accelerator (microtron) were used as the electron beam sources. The analysis of the behaviour of the measured glutamine molecule mass-spectra irradiated at the above doses demonstrates, as compared to the irradiated molecule mass-spectrum, that the high-energy irradiation of the initial molecule results in the irreversible changes of its structure.

Fragmentations of Deprotonated Alkyl Hydroperoxides (ROO− Upon Collisional Activation: A Combined Experimental and Computational Study

The collision-induced dissociation (CID) mass spectra of the [M − H]– anions of methyl, ethyl, and tert-butyl hydroperoxides have been measured over a range of collision energies in a flowing afterglow–selected ion flow tube (FA-SIFT) mass spectrometer. Activation of the CH3OO– anion is found to give predominantly HO– fragment anions whilst CH3CH2OO− and (CH3)3COO– produce HOO– as the major ionic fragment. These results, and other minor fragmentation pathways, can be rationalized in terms of unimolecular rearrangement of the activated anions with subsequent decomposition. The rearrangement reactions occur via initial abstraction of a proton from the α-carbon in the case of CH3OO– or the β-carbon for CH3CH2OO– and (CH3)3COO–. Electronic structure calculations suggest that for the CH3CH2OO– anion, which can theoretically undergo both α- and β-proton abstraction, the latter pathway, resulting in HOO– + CH2CH2, is energetically preferred.

Highly charged ions from rare gas and metal clusters in intense laser fields

Rare gas or lead clusters of several hundreds to many thousands of atoms per cluster were irradiated by intense laser pulses producing peak intensities up to 1017W/cm2. Fast, highly charged fragment ions were observed by means of standard TOF mass spectrometry as well as a magnetic deflection TOF device (MDTOF). Charge states of up to Xe30+ or Pb18+ were detected with maximum kinetic energies reaching far beyond 100 keV for Xe. A strong dependence of the charging and heating process on the laser pulse duration was found. While the resulting ionic fragment spectra are qualitatively similar for rare gas and lead clusters, the kinetic energies for the metal clusters seem to be significantly lower.