Energias de aparecimento e expoentes de Wannier de fragmentos iônicos do sec-butanol

Abstract

In this work, the Mass Spectrum (MS) and the Appearance Energy (AE) values of the ionic fragments formed in electron collisions with sec-butanol (or 2- butanol) were studied using a HIDEN Mass Spectrometer EPIC300. The MS was acquired for electron impact energy of 70 eV, with a mass resolution of 1 a.m.u. (atomic mass unit). The AEs were determined from the acquisition of ionic fragmentation curves of sec-butanol for the electron impact energies covering the region from the ionic fragment, formation threshold up to about ten eV above this value. The extended Wannier Law convoluted with the Gaussian dispersion of the energy of the incident electrons on the sec-butanol was applied to obtain the ionic fragmentation function, which was adjusted to the experimental data to obtain the AE’s. The Mass Spectrometer recorded 54 ionic fragments, distributed in 6 groups of peaks, 30 of them with abundances above than 1% and only the base peak with abundances greater than 50%. The intensity of the spectrum was normalized taking as a reference the base peak, attributed to the formation of the ion C2H5O+ , observed at 45 a.m.u.. The peak responsible for the formation of monocharged sec-butanol (C4H10O+ ) has a low abundance, indicating its high instability. The EM resolution obtained in this work and the number of peaks observed are much higher than the data reported in the literature, most likely due to the high resolution of the apparatus used. The attribution of the peaks observed in EM to the cations formed in the collision of electrons with sec-butanol is reported, and for some of them, we present a tentative assignment, since their mass/charge ratios may correspond to the formation of different cations. The AE's and Wannier coefficients (p) of the fragments recorded in the EM with relative intensities greater than 5 a.m.u. were determined, totaling 16 fragments, 12 of which were reported for the first time in the literature.