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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Solid state and solution nitrate photochemistry: Photochemical evolution of the solid state lattice
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Solid state and solution nitrate photochemistry: Photochemical evolution of the solid state lattice

机译：固态和溶液硝酸盐光化学：固态晶格的光化学演化

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We examined the deep UV 229 nm photochemistry of NaNO_3 in solution and in the solid state. In aqueous solution excitation within the deep UV NO_3~- strong π → π* transition causes the photochemical reaction NO_3~- → NO_2~- + O·. We used UV resonance Raman spectroscopy to examine the photon dose dependence of the NO_2~- band intensities and measure a photochemical quantum yield of 0.04 at pH 6.5. We also examined the response of solid NaNO_3 samples to 229 nm excitation and also observe formation of NO_2~-. The quantum yield is much smaller at ～10~(-8). The solid state NaNO_3 photochemistry phenomena appear complex by showing a significant dependence on the UV excitation flux and dose. At low flux/dose conditions NO_2~- resonance Raman bands appear, accompanied by perturbed NO_3~- bands, indicating stress in the NaNO_3 lattice. Higher flux/dose conditions show less lattice perturbation but SEM shows surface eruptions that alleviate the stress induced by the photochemistry. Higher flux/dose measurements cause cratering and destruction of the NaNO_3 surface as the surface layers are converted to NO_2~-. Modest laser excitation UV beams excavate surface layers in the solid NaNO_3 samples. At the lowest incident fluxes a pressure buildup competes with effusion to reach a steady state giving rise to perturbed NO_3~- bands. Increased fluxes result in pressures that cause the sample to erupt, relieving the pressure.
机译：我们检查了NaNO_3在溶液和固态中的深229 nm紫外光化学性质。在水溶液中，在深紫外光中，NO_3〜-强烈的π→π*跃迁引起光化学反应NO_3〜-→NO_2〜-+ O·。我们使用紫外共振拉曼光谱法研究了NO_2〜-谱带强度的光子剂量依赖性，并在pH 6.5下测量了0.04的光化学量子产率。我们还检查了固体NaNO_3样品对229 nm激发的响应，并观察到NO_2〜-的形成。量子产率在〜10〜（-8）小得多。固态NaNO_3光化学现象通过显示对紫外激发通量和剂量的显着依赖性而显得复杂。在低通量/剂量条件下，出现NO_2〜-共振拉曼带，并伴有扰动的NO_3〜-带，表明NaNO_3晶格中存在应力。较高的通量/剂量条件显示较少的晶格扰动，但SEM显示的表面喷发减轻了光化学引起的应力。当表面层转化为NO_2〜-时，较高的通量/剂量测量值会导致NaNO_3表面的凹陷和破坏。适度的激光激发UV光束可以挖掘固体NaNO_3样品中的表面层。在最低的入射通量下，压力累积与渗出竞争，达到稳态，从而引起扰动的NO_3〜-谱带。通量增加会导致压力，导致样品喷发，从而释放压力。

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