Two-Color Symmetry Breaking in Laser-Based Secondary Neutral Mass Spectrometry.

Rationale An alternative method of analysis for laser-based secondary neutral mass spectrometry is introduced. Methods By mixing a fundamental 1240 nm wavelength of the near-infrared laser field with an intensity of 1 x 10(15) W/cm(2)with its second harmonic generation wavelength of 620 nm, control is attained over the ion yield in secondary neutral mass spectrometry for a native silver surface and a surface covered with silver nanoparticles. Results The ion yields of selected species in the mass spectra, such as a C(2)H(4)O(2)surfactant fragment ion and the Ag ion, are enhanced or suppressed by a factor of 8 or 23, respectively, in comparison with single color post-ionization. In addition, a significant suppression of ion fragmentation is demonstrated for both the silver sample and silver nanoparticles. Periodic variation of the ion yield with a modulation depth of 4% is observed depending upon the relative phase between the fundamental and second harmonic generated fields. These variations are explained in terms of tunneling ionization with symmetry-broken fields. Conclusions An additional degree of freedom in a form of additional second color is introduced in laser-based secondary neutral mass spectrometry. Ion yield control is extended in a form of symmetry-broken fields.