Dissociative photoionization of isoprene: experiments and calculations

Abstract

Vacuum ultraviolet (VUV) dissociative photoionization of isoprene in the energy region 8.5-18 eV was investigated with photoionization mass spectroscopy (PIMS) using synchrotron radiation (SR). The ionization energy (IE) of isoprene as well as the appearance energies (AEs) of its fragment ions C(5)H(7) (+), C(5)H(5) (+), C(4)H(5) (+), C(3)H(6) (+), C(3)H(5) (+), C(3)H(4) (+), C(3)H(3) (+) and C(2)H(3) (+) were determined with photoionization efficiency (PIE) curves. The dissociation energies of some possible dissociation channels to produce those fragment ions were also determined experimentally. The total energies of C(5)H(8) and its main fragments were calculated using the Gaussian 03 program and the Gaussian-2 method. The IE of C(5)H(8), the AEs for its fragment ions, and the dissociation energies to produce them were predicted using the high-accuracy energy model. According to our results, the experimental dissociation energies were in reasonable agreement with the calculated values of the proposed photodissociation channels of C(5)H(8).

Vacuum ultraviolet photoionization mass spectrometric study of cyclohexene

“…It should be noted that the thermal energy distribution of the parent molecule is not taken into account in our data processing, in view of the nozzle supersonic expansion condition mentioned above. In addition, no correction is made for possible kinetic shifts in determining the AEs …”

Photoionization and dissociation of the monoterpene limonene: mass spectrometric and computational investigation

“…The experimental apparatus has been described previously . In brief, we performed photoionization mass spectrometric measurements on the Atomic and Molecular Physics Beamline (U14‐A) with a supersonic expansion molecular beam/reflectron TOF mass spectrometer (RTOFMS) system at the National Synchrotron Radiation Laboratory in Hefei, China.…”

“…The experimental apparatus has been described previously. [17][18][19][20][21] In brief, we performed photoionization mass spectrometric measurements on the Atomic and Molecular Physics Beamline (U14-A) with a supersonic expansion molecular beam/reflectron TOF mass spectrometer (RTOFMS) system at the National Synchrotron Radiation Laboratory in Hefei, China. The synchrotron radiation beam from an undulator of the 800 MeV electron storage ring of the NRSL is monochromatized with a 6 m length monochromator equipped with three gratings (1250, 740 and 370) lines/mm.…”

The use of isoprene as a novel dopant in negative ion atmospheric pressure photoionization mass spectrometry coupled to high‐performance liquid chromatography

“…In this study, we primarily evaluated the potential of monoterpenes including limonene, α‐pinene, and p ‐cymene and their structural unit, isoprene, as dopants for APPI. According to data available on photoabsorption cross sections, these species absorb the VUV photons from the krypton lamp as effectively as toluene and do not have positive electron affinities . Moreover, these compounds are natural compounds ubiquitous in nature and are considered less hazardous .…”