Thøgersen Jan, Weidner Tobias, Jensen Frank
Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Phys Chem Chem Phys. 2022 Oct 19;24(40):24695-24705. doi: 10.1039/d2cp03166c.
We study the primary dissociation dynamics of aqueous formamide (HCONH) and dimethylformamide (HCON(CH)) induced by photo-excitation at = 200 nm. The photolysis is recorded with sub-picosecond time resolution by UV pump-IR probe transient absorption spectroscopy. Formamide dissociates with a quantum yield of ( = 20 ps) = 0.30 ± 0.05, = 20 ps after the excitation. The rest of the excited formamide molecules return to the ground state within = 1 ps and vibrationally relax towards equilibrium in ≈ 10 ps. The only product observed is NH. NH is produced with a yield of (NH) = 0.23 ± 0.10 on a timescale of = 3 ± 1 ps and likely constitutes the dominating product. The CO counter product to NH is not observed. Dimethylformamide is photolysed with a quantum yield of ( = 30 ps) = 0.29 ± 0.05, = 30 ps after the excitation. The photolysis of dimethylformamide produces CO on a time scale of ≈ 30 ps. The data indicate that dimethylamine and the N(CH) radical are likely photoproducts.
我们研究了在波长λ = 200 nm的光激发下，甲酰胺（HCONH₂）和二甲基甲酰胺（HCON(CH₃)₂）的初级解离动力学。通过紫外泵浦 - 红外探测瞬态吸收光谱，以亚皮秒时间分辨率记录光解过程。甲酰胺在激发后20皮秒时的量子产率为Φ(τ = 20 ps) = 0.30 ± 0.05。其余被激发的甲酰胺分子在1皮秒内返回基态，并在约10皮秒内振动弛豫至平衡态。观察到的唯一产物是NH₃。NH₃在τ = 3 ± 1皮秒的时间尺度上以产率Φ(NH₃) = 0.23 ± 0.10产生，并且可能是主要产物。未观察到与NH₃对应的CO产物。二甲基甲酰胺在激发后30皮秒时的量子产率为Φ(τ = 30 ps) = 0.29 ± 0.05。二甲基甲酰胺的光解在约30皮秒的时间尺度上产生CO。数据表明二甲胺和N(CH₃)自由基可能是光解产物。
