ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
To select the substrate metal best for producing thermal positive ions from incident sample molecules, a beam of diatomic molecule (MX) such as LiCl, NaBr, or TlCl was directed with a constant flux (∼1012–1014 molecules cm−2 s−1) onto a polycrystalline thin wire (∼0.01–0.02 cm in diameter) of refractory metal (Nb, Mo, Ta, W, Re, Ir, or Pt) heated in vacuum (∼10−7–10−5 Torr), and the total emission current (∼10−10–10−8 A) of the positive ion (M+) was measured as a function of wire temperature (∼900–2300 K). The experimental data newly achieved were analyzed by our theoretical model to determine the ionization efficiency (β+) and also the work function (φ+) effective for the ionization. Among the seven metals, Re is concluded to be best for the ionization because Re is highest in φ+(∼7.5 eV), thereby making it possible to produce M+ efficiently (β+=1) and stably (within ±1%) from those 30 elements (M) whose ionization energy is less than ∼6.5 eV. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1150312
Permalink