Collision Energy Values Research Articles

Classical trajectory picture of the autoionization event in He(2 3S)–D 2 Penning ionization: collision energy dependence

A theoretical picture of the dynamics of the autoionization event He(2 3S)–D 2( v″=0) → [He…D 2 +( v′)]+e − is obtained for the values of collision energy ranging from 20 to 150 meV. The treatment of the dynamics consists in 2D classical trajectory calculations based on static characteristics which include quantum mechanical treatment of the perturbed D 2( v″=0) and D 2 +( v′) vibrational motion. The vibrational populations are dynamical averages over the local widths of the He(2 3S)–D 2( v″=0) state with respect to autoionization to D 2 +(…He) in its v′th vibrational level, the Penning electron energies are related to the local differences between the energies of the corresponding perturbed D 2( v″=0)(…He *) and D 2 +( v′)(…He) vibrational states. In accordance with recent experimental data on the He(2 3S)–H 2( v″=0) isotopic variant of the system, the average Penning electron energies are found to increase smoothly with increasing collision energy and the vibrational populations for the nascent Penning ions D 2 +( v′)(…He) are predicted to be nearly independent of the collision energy.

Reproducing daughter‐ion spectra using the transmission oscillation properties of quadrupole collision cells

AbstractThe transmission oscillation properties of parent ions through an RF‐only quadrupole are investigated as a function of collision energy, radicfrequency of the quadrupole, and type and pressure of target gas. It is shown that small variations of collision energy can result in substantial differences in daughter‐ion spectra obtained from the same parent ion. Since absolute values of collision energy are difficult to determine, reproducible daughter‐ion spectra are problematical to acquire.In this work we show that reproduction of daughter‐ion spectra, using the transmission properties of the collision cell, is possible. The characteristics of an RF‐only quadrupole (Q*) are such that the parent ion intensity at the second detector varies as a function of collision energy and displays sinusoidal properties. By using the nodes and anti‐nodes of the parent‐ion transmission it is possible to achieve reproducible daughter‐ion spectra of a wide range of biopolymers. The tuning of Q* is mass‐dependent and not compound‐dependent. Hence it is possible to optimize and tune Q* using an isobaric (or almost) standard such as one of the ions of perfluorotri‐n‐butylamine (electron ionization) or a glycerol cluster ion (fast‐atom bombardment mass spectrometry) before subjecting valuable sample to tandem mass spectrometry.