Fournier I, Marinach C, Tabet J C, Bolbach G
Laboratoire de Chimie Structurale Organique et Biologique, Université P and M Curie, Paris, France.
J Am Soc Mass Spectrom. 2003 Aug;14(8):893-9. doi: 10.1016/S1044-0305(03)00347-7.
Irradiation effects at low and high laser fluence on 2,5-dihydroxybenzoic acid large crystals were investigated. Contrary to what was observed for matrices as cinnamic acid derivatives, no chemical degradation of matrix is evidenced and continuous ablation as well as ion production resulted of extended irradiation in all the fluence range corresponding to classical matrix-assisted laser desorption /ionization. Ripples are formed on the base of the crater for a limited number of laser shots under moderate fluence. For extended irradiation, conical shape craters are formed with the axis of the crater oriented along the incident direction of the laser beam. A study of the craters showed that ablation through the ablated volume slowly varied with the laser fluence when a strong increase of ion production (matrix and analyte) was recorded. Ablation volume was found to vary non-linearly with the number of laser shots. On a same spot, the ablated volume and the ion production were measured as a function of the laser energy. With an increasing laser energy (or fluence), the ablated volume slowly increases when the ion production strongly increases. This gives evidence of a decoupling between ablation and ionization. Interaction of the plume with the incoming beam is thus probable.
研究了低激光能量密度和高激光能量密度下2,5 - 二羟基苯甲酸大晶体的辐照效应。与肉桂酸衍生物等基质所观察到的情况相反，未发现基质有化学降解现象，并且在对应于传统基质辅助激光解吸/电离的所有能量密度范围内，长时间辐照会导致持续烧蚀以及离子产生。在中等能量密度下，有限次数的激光照射会在坑底形成波纹。对于长时间辐照，会形成锥形坑，坑的轴线沿激光束的入射方向。对坑的研究表明，当记录到离子产生（基质和分析物）大幅增加时，通过烧蚀体积的烧蚀随激光能量密度缓慢变化。发现烧蚀体积随激光照射次数呈非线性变化。在同一点上，测量了烧蚀体积和离子产生量随激光能量的变化。随着激光能量（或能量密度）增加，当离子产生量大幅增加时，烧蚀体积缓慢增加。这证明了烧蚀和电离之间的解耦。因此，羽流与入射光束之间可能存在相互作用。
