In this work, by capitalizing on the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) methods, it has been systematically studied that the excited state double intramolecular proton transfer (ESDPT) process and the photophysical properties of 1,8-dihydroxy-2-naphthaldehyde (DHNA) are affected by the distinct external electric fields (EEFs). The obtained intramolecular hydrogen bond (IHB) parameters containing bond lengths and angles, as well as infrared (IR) vibrational spectra demonstrate that IHB strength changes in the distinct EEFs. Moreover, not only do the potential energy surfaces (PESs) indicate that the ESDPT process of DHNA is stepwise, but also increasing the positive EEF results in a decrease in the energy barrier accordingly, while vice versa. The absorption and fluorescence spectra also undergo a corresponding red or blue shift in the EEF; for instance, when the EEF changes from +10 × 10⁻⁴ a.u. to +20 × 10⁻⁴ a.u., the fluorescence peak undergoes a blue shift from 602 nm to 513 nm in the keto2 form. In a nutshell, the ESDPT process of DHNA can be influenced by the EEF, which will serve as a reference in regulating and controlling proton transfer that causes luminescence.

中文翻译：

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外电场对1,8-二羟基-2-萘醛ESDPT过程和光物理性质的影响


本工作利用密度泛函理论（DFT）和瞬态密度泛函理论（TD-DFT）方法，系统研究了激发态双分子内质子转移（ESDPT）过程及其光物理性质。 1,8-二羟基-2-萘醛 (DHNA) 受到不同外部电场 (EEF) 的影响。获得的包含键长和角度的分子内氢键 (IHB) 参数以及红外 (IR) 振动光谱表明不同 EEF 中 IHB 强度的变化。此外，势能面（PES）不仅表明DHNA的ESDPT过程是逐步的，而且增加正EEF会导致能垒相应降低，反之亦然。 EEF 中的吸收光谱和荧光光谱也会发生相应的红移或蓝移；例如，当EEF从+10 × 10 ^-4 au变化到+20 × 10 ^-4 au时，酮2形式的荧光峰从602 nm蓝移到513 nm。简而言之，DHNA的ESDPT过程可以受到EEF的影响，这将作为调控引起发光的质子转移的参考。