Ion Source in Negative Ion Lifetime Measurements of Resonance Electron Capture by Molecules

Formation, autoionization, and lifetime of long-lived negative molecular ions of nitrobenzene (C6H5NO2) formed by resonance capture were studied using a static mass spectrometer MI-1201V, reequipped for these purposes. An additional modification of the ion source was carried out in order to exclude the ion desorbed from the chamber walls from entering the ion beam emerging from the slit of the ionization chamber cover, which resulted in distortion of the ion lifetime (τa) measurement results. The absence of the temperature dependence of the ion lifetime in the range of (393–473 K) was confirmed, which, on the one hand, indicates the effective exclusion of the integration of desorbed ions into the ion beam emerging from the slit of the ionization chamber cover, and, on the other hand, gives the correct value of τa = 50.0 ± 1.0 μs.