APPEARANCE POTENTIALS OF POSITIVE AND NEGATIVE IONS BY MASS SPECTROMETRY

Appearance potentials (AP) of ions were obtained by the retarding potential difference (RPD) technique using a time‐of‐flight mass spectrometer. Confirmatory measurements were made using a 180° magnetic instrument. Information about processes such as ion‐pair formation, electronic excitation of ions, rearrangement of ions, autoionization and metastable transitions is inferred from the structure of the ionization efficiency (IE) curves of Xe, H2, CH4, CD4, C2H4, C2H6, C3H8, and C4H10 over about a 4 eV range. The AP's in Xe at 12.02, 12.35, 12.75, and 14.0 correspond in a qualitative way to autoionization levels. The structure observed in parent and fragment IE curves for hydrocarbons can, in some systems, be correlated with known processes. Structure due to vibrational excitation of ions was not resolved. The IE curves for polyatomic ions indicate that many ions formed by electron impact are formed in electronically excited states, and that appearance potentials of fragment ions often correlate with upward...

[1]  S. Rice,et al.  Mass Spectrometry of Organic Ions , 1964 .

[2]  A. Nicholson.  Photo‐Ionization Efficiency Curves. Measurement of Ionization Potentials and Interpretation of Fine Structure , 1963 .

[3]  John F. Burns.  Experimental Detection of Auto-Ionizing Transitions in Krypton by Electron Impact , 1961, Nature.

[4]  B. H. Nall,et al.  Structure in the Ionization Near Threshold of Rare Gases by Electron Impact , 1961 .

[5]  B. Steiner,et al.  Photoionization of Alkanes. Dissociation of Excited Molecular Ions , 1961 .

[6]  J. D. Morrison,et al.  Threshold Law for the Probability of Excitation of Molecules by Photon Impact. A Study of the Photoionization Efficiencies of Br2, I2, HI, and CH3I , 1960 .

[7]  J. D. Morrison,et al.  THRESHOLD LAW FOR THE PROBABILITY OF EXCITATION BY ELECTRON IMPACT , 1960 .

[8]  H. Eyring,et al.  Mass Spectrum of Propane: Isotope Effect and Metastable Ions , 1960 .

[9]  H. Schiff,et al.  Electron Impact Study of Nitric Oxide Using a Modified Retarding Potential Difference Method , 1959 .

[10]  M. Wolfsberg,et al.  Variation of Appearance Potentials of Alkane Fragment Ions with the Repeller Voltage of the Mass Spectrometer Ion Source , 1959 .

[11]  F. W. Lampe,et al.  Reactions of Gaseous Ions. VI. Hydride Ion Transfer Reactions , 1958 .

[12]  D. C. Frost,et al.  EXCITED STATES OF THE MOLECULAR IONS OF HYDROGEN FLUORIDE, HYDROGEN IODIDE, WATER, HYDROGEN SULPHIDE, AND AMMONIA , 1958 .

[13]  Toshio Nakayama,et al.  Ionization Potentials of Some Molecules , 1957 .

[14]  D. C. Frost,et al.  Studies of the ionization of molecules by electron impact I. Excited states of the nitrogen molecular ion , 1955, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[15]  E. Clarke.  IONIZATION PROBABILITY CURVES USING AN ELECTRON SELECTOR: RESULTS ON N2+, N+, Xe++ , 1954 .

[16]  D. J. Grove,et al.  IONIZATION POTENTIALS AND PROBABILITIES USING A MASS SPECTROMETER , 1951 .

[17]  L. G. Smith.  Ionization and Dissociation of Polyatomic Molecules by Electron Impact. I. Methane , 1937 .