A new organic ionic crystal of 4-(dimethylamino)-1-ethylpyridinium iodide (DMAEPI) was synthesized for use in second-order nonlinear optics, and its crystal structure was found to belong to the orthorhombic space group Pmn21. This crystal is considered to be a promising candidate for frequency conversion of diode lasers, since it has an estimated off-diagonal component of second-harmonic coefficient (d) which is about three-fourths that of the yellowish (4-nitrophenyl)-L-prolinol (NPP) irrespective of the cutoff wavelength at approximately 390 nm.

中文翻译：

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4-(二甲氨基)-1-乙基吡啶碘化物：一种用于二阶非线性光学的新型无色有机离子晶体

合成了一种用于二阶非线性光学的新型有机离子晶体 4-(二甲氨基)-1-乙基吡啶鎓碘化物 (DMAEPI)，发现其晶体结构属于正交空间群 Pmn21。这种晶体被认为是二极管激光器频率转换的有希望的候选者，因为它具有二次谐波系数 (d) 的估计非对角线分量，约为淡黄色 (4-硝基苯基)-L 的四分之三-脯氨醇 (NPP)，与大约 390 nm 处的截止波长无关。