AU+, AG+ AND CU+ ATTACHMENT TO POLYBUTADIENE IN LASER DESORPTION AT 1064-NM

Cu+, Ag+ and Au+ gas-phase ions have been found, in laser desorption time-of-flight experiments, to attach efficiently to polybutadiene, a polymer containing no polar groups. The desorption and cation attachment were accomplished using the fundamental frequency of a Nd:YAG laser, at a wavelength of 1064 nm, and supporting the samples on probe tips made of the appropriate metal. Laser powers were in the range of 1.0-2.0 X 10(8) W/cm2. Time delays between the application of the laser pulse and the sampling of the resultant ion population were in the range 30-80 mus. The Au+ attachment is contrary to the reported findings from a laser desorption charge-exchange spectrum obtained from a gold surface by Kahr and Wilkins. The differences in the spectra are discussed in terms of the differences in the two experimental methods. Attachment by these ions could be useful in the laser desorption analysis of other polymer molecules, particularly those containing no polar groups.