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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photoionization-induced water migration in the hydrated trans-formanilide cluster cation revealed by gas-phase spectroscopy and Ab initio molecular dynamics simulation
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Photoionization-induced water migration in the hydrated trans-formanilide cluster cation revealed by gas-phase spectroscopy and Ab initio molecular dynamics simulation

机译：气相色谱法和从头算分子动力学模拟揭示水合反式甲酰苯胺簇阳离子中光电离诱导的水迁移

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摘要

Photoionization-induced water migration in the trans-formanilide-water 1:1 cluster, FA-(H _2O) _1, has been investigated by using IR-dip spectroscopy, quantum chemical calculations, and ab initio molecular dynamics simulations. In the S _0 state, FA-(H _2O) _1 has two structural isomers, FA(NH)-(H _2O) _1 and FA(CO)-(H _2O) _1, where a water molecule is hydrogen-bonded (H-bonded) to the NH group and the CO group, respectively. In addition, the S _1-S _0 origin transition of FA(CO)-(H _2O) _2, where a water dimer is H-bonded to the CO group, was observed only in the [FA-(H _2O) _1] ~+ mass channel, indicating that one of the water molecules evaporates completely in the D _0 state. These results are consistent with a previous report [Robertson, E. G. Chem. Phys. Lett., 2000, 325, 299]. In the D _0 state, however, [FA-(H _2O) _1] ~+ produced by photoionization via the S _1-S _0 origin transitions of FA(NH)-(H _2O) -1 and FA(CO)-(H _2O) _1 shows essentially the same IR spectra. Compared with the theoretical calculations, [FA-(H _2O) _1] ~+ can be assigned to [FA(NH)-(H _2O) _1] ~+. This means that the water molecule in [FA-(H _2O) _1] ~+ migrates from the CO group to the NH group when [FA-(H _2O) _1] ~+ is produced by photoionization of FA(CO)-(H _2O) _1. [FA-(H _2O) _1] ~+ produced by photoionization of FA(CO)-(H _2O) _2 also shows the IR spectrum corresponding to [FA(NH)-(H _2O) _1] ~+. In this case, the water migration from the CO group to the NH group occurs with the evaporation of a water molecule. Ab initio molecular dynamics simulations revealed the water migration pathway in [FA-(H _2O) _1] ~+. The calculations of classical electrostatic interactions show that charge-dipole interaction between FA ~+ and H _2O induces an initial structural change in [FA-(H _2O) _1] ~+. An exchange repulsion between the lone pairs of the CO group and H 2O in [FA-(H _2O) _1] ~+ also affects the initial direction of the water migration. These two factors play important roles in determining the initial water migration pathway.
机译：通过使用红外浸没光谱，量子化学计算和从头算分子动力学模拟研究了反式甲酰苯胺-水1：1簇FA-（H _2O）_1中光电离诱导的水迁移。在S _0状态下，FA-（H _2O）_1具有两个结构异构体FA（NH）-（H _2O）_1和FA（CO）-（H _2O）_1，其中水分子与氢键结合（H （键合）到NH基团和CO基团上。另外，仅在[FA-（H _2O）_1]中观察到FA（CO）-（H _2O）_2的S _1-S _0原点转变，其中水二聚体与CO基团H键合。 〜+质量通道，表明其中一个水分子在D _0状态下完全蒸发。这些结果与先前的报告一致[Robertson，E.G.Chem。物理Lett。，2000，325，299]。然而，在D _0状态下，通过FA（NH）-（H _2O）-1和FA（CO）-（的S _1-S _0起源跃迁通过光电离产生的[FA-（H _2O）_1]〜+ H _2O）_1显示基本相同的IR光谱。与理论计算相比，可以将[F​​A-（H _2O）_1]〜+分配给[FA（NH）-（H _2O）_1]〜+。这意味着当通过FA（CO）-的光电离产生[FA-（H _2O）_1]〜+时，[FA-（H _2O）_1]〜+中的水分子从CO基团迁移到NH基团。 H _2O）_1。通过FA（CO）-（H _2O）_2的光电离产生的[FA-（H _2O）_1]〜+还显示对应于[FA（NH）-（H _2O）_1]〜+的红外光谱。在这种情况下，水从CO基团向NH基团的迁移随水分子的蒸发而发生。从头算分子动力学模拟揭示了[FA-（H _2O）_1]〜+中水的迁移路径。经典静电相互作用的计算表明，FA〜+与H _2O之间的电荷-偶极相互作用引起[FA-（H _2O）_1]〜+中的初始结构变化。 [FA-（H _2O）_1]〜+中CO基团与H 2O的孤对之间的交换排斥力也会影响水迁移的初始方向。这两个因素在确定初始水迁移路径中起着重要作用。

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