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3D-O1-0920 PDF
紫外レーザーポストイオン化法を用いたMALDI法における相爆発過程の検証
Neutral 2,5-dihydroxy benzoic acid (DHB) in the MALDI plume was probed by UV laser post-ionization. DHB+ (m 154), dehydrated ions [DHB-H2O]+ (m 136) were detected as the neutral DHB-derived ions and decarbonated ions [DHB-CO2]+ (m 110) was detected as the neutral dehydrated DHB-derived ions by a time-of-flight mass spectrometer. With increasing delay time between lasers, the ratio m136/m154 decreases and converges to a constant value, while the ratio m110/m154 increases and converges to a constant value. This result indicates that the highly excited neutral DHB molecules remain without sufficient energy relaxation through collisions in the front part of the plume, while the energy relaxation sufficiently proceeds, and the overall temperature rises higher than the pyrolysis temperature in the rear part of the plume, resulting in the phase explosion.