Fernández-Lima F A, Ponciano C R, da Silveira E F
Instituto Superior de Tecnologias y Ciencias Aplicadas, Havana, Cuba.
J Mass Spectrom. 2008 May;43(5):587-93. doi: 10.1002/jms.1350.
Time of flight-mass spectrometry (TOF-MS) is used to analyze positive and negative desorbed ions generated by UV laser ablation of several alkali (X) halide (Y) salts. Most of the observed desorbed cluster ions have the structure (XY)(n)X(+) or (XY)(n)Y(-). Their desorption yields decrease as exp(-kn), where k approximately 2 for both series, suggesting that the neutral component (XY)(n) plays the dominant role in the desorption process. Mass spectrum measurements were performed for compound samples in which two salts (out of CsI, RbI, KBr, KCl and KI) are homogeneously mixed or disposed in two superposed layers. The detection of small new ion species and large cluster ions of the original salts supports the scenario that the uppermost layers are completely atomized while deep layers are emitted colder and fragmented: It is proposed that ns-pulsed laser induced desorption of ionic salts occurs via two sequential mechanisms: (1) ejection of cations and anions in the hot plume, followed by recombination into new cluster ions and (2) ejection of relatively cold preformed species originated from deep layers or from periphery of the irradiated region.
飞行时间质谱（TOF-MS）用于分析由几种碱金属（X）卤化物（Y）盐的紫外激光烧蚀产生的正负解吸离子。观察到的大多数解吸簇离子具有（XY）(n)X⁺或（XY）(n)Y⁻的结构。它们的解吸产率以exp(-kn)的形式下降，其中两个系列的k约为2，这表明中性成分（XY）(n)在解吸过程中起主导作用。对复合样品进行了质谱测量，其中两种盐（CsI、RbI、KBr、KCl和KI中的两种）均匀混合或置于两个叠加层中。对原始盐的小新离子物种和大簇离子的检测支持了这样一种情况：最上层完全原子化，而深层发射时温度较低且发生碎片化：有人提出，ns脉冲激光诱导的离子盐解吸通过两种连续机制发生：（1）热羽流中阳离子和阴离子的喷射，随后重组为新的簇离子；（2）喷射源自深层或辐照区域周边的相对较冷的预形成物种。
