Electron impact ionization of spatially oriented CH3Cl and CCl3H

Absolute electron impact ionization cross-sections for the C1 to C4 alcohols

“…1 There have been few studies on the influence of functional group, molecular shape and size, molecular orientation and three-dimensional structure on ionization efficiency. [2][3][4][5][6][7][8][9] Accurate measurements of the total ionization cross-section can be used together with empirical and theoretical relationships to estimate unknown values for other molecular parameters, such as molecular polarisability, and may be used to test theoretical predictions. 10,11 Electron impact ionization plays an important role in many areas of chemistry and physics, including mass spectrometry, plasma processes and gas discharges.…”

Generation, characterisation, and applications of atomic and molecular alignment and orientation

“…At an electron energy of 200 eV, production of the molecular ion, CH 3 Cl + , was found to be 2.6 times more likely when the electron was incident on the positive (CH 3 ) end of the molecular dipole than on the negative (Cl) end. The steric effect has been reproduced by several theoretical models, 27,63,64 and may be interpreted in terms of the more attractive nature of the interaction potential between the electron and molecule when the negatively charged electron interacts with the positively charged end of the molecular dipole. Interestingly, at lower electron energies the steric effect is reduced.…”

“…However, a number of studies employing the hexapole orientation method have shown clear steric preferences for reaction at one end of a symmetric-top molecule over the other. [25][26][27] 2.3 Alignment using a strong laser field…”

“…Harland and coworkers have studied the orientation dependence of the electron impact process for CH 3 Cl, along with several other symmetric top molecules. 26,27 An oriented beam of CH 3 Cl was prepared using the hexapole method and crossed at right angles with an electron beam. The resulting ions were detected by a quadrupole mass spectrometer.…”

Ionization Surfaces for Small Molecules

“…A recent cross-particle beam experiment has shown that the cross section for electron impact ionization of several symmetric top molecules is dependent on the electron-molecule orientation. 6,7 For example, the ratio of molecular ion formation, CH 3 Cl + , for collisions of electrons on the CH 3 -end of the CH 3 Cl molecule was 2.6 times higher than that for collisions on the Cl-end of the molecule, while for total ionization this ratio is close to 1.6. This suggests that molecules exhibit a shape with respect to electron impact ionization.…”