Sputtered protons during surface-induced dissociation (SID) tandem mass spectrometry (MS/MS)

• Published in: International journal of mass spectrometry and ion processes Vol. 148; no. 1; pp. 25 - 30
• Main Authors: Hayward, Mark J., Park, Frederick D.S., Manzella, Lynn M., Bernasek, Steven L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 29.09.1995
• Subjects: Charge exchange; Sputtering; Surface-induced dissociation; Ultrahigh vacuum; Surface-induced dissociation; Charge exchange; Ultrahigh vacuum; Sputtering
• ISSN: 0168-1176; 1873-2801
• DOI: 10.1016/0168-1176(95)04178-N

A new tandem mass spectrometer has been constructed for the study of ion/surface interactions and the study of surface induced dissociation processes. During the development and initial testing of this new instrument, experiments have been carried out using a stainless steel surface under high vacuum (10 −7-10 −8 Torr) conditions where hydrocarbons (pump oil) would be expected to be adsorbed onto the surface. A surprising result of these experiments has been the observation of sputtered protons. The yield of sputtered protons remains relatively constant with varying incident ion kinetic energy (over the 20–100 eV range) and appears to have little or no dependence on momentum transfer from the incident ions. These findings provide direct evidence (via observation of an excess of the charged intermediate protons) for a charge exchange mechanism for associative ion/surface reactions involving protonation. However, the yield of protonated products (protonated pyridazine ions) due to associative ion/surface reactions is dependent on incident ion kinetic energy. These results suggest that the protonation of pyridazine may depend on interaction times at the surface which, in turn, depend on the depth of penetration of the incident species into the hydrocarbon overlayer. In addition, the observation of sputtered protons as the likely intermediates to associative ion/surface protonation reactions may have implications for the proposed mechanisms of ion/surface reactions where alkylation of incident ions occurs.