Mercurymono oxide cluster ions (HgO)_n~+ by laser desorption ionization time of flight mass spectrometry

摘要

Small quantity (few milligrams) of spectroscopic pure HgO powder (Jhonson Matthey & Co., Ltd, London) was placed over 1-2 μL of deionized water on a stainless steel surface and allowed to dry at room temperature. The air dried sample was analyzed using an indigenously developed 3-m long linear TOFMS. The resolving power of the TOFMS is found to be 600 (full width at half maximum) at 200 amu. Laser radiation with pulse energy of 20 μJ obtained from a frequency tripled Nd:YAG laser (λ = 355 nm, τ = 3 ns) was focused to ~200 μm on the sample surface. The ions generated by dissociation/desorption/ionization of solid HgO are promptly accelerated and extracted by the application of DC electric field of 20 and 10 kV, respectively. The positive ions detected by a microchannel plate detector are further amplified by a preamplifier. The signal acquired through a digital storage oscilloscope are converted into mass spectra and calibrated.