The dissociation dynamics of CH₃I at three UV pump wavelengths (279nm, 254nm, 243nm) are measured using an extreme ultraviolet probe in a time-resolved photoelectron spectroscopy experiment. The results are compared with previously published data at a pump wavelength of 269nm, [2020, Phys. Chem. Chem. Phys., 22, 25695], with complementary photoelectron spectroscopy experiments performed using a multiphoton ionization (MPI) probe [2019, Phys. Chem. Chem. Phys., 21, 11142] and with the recent action spectroscopy measurements of Murillo-Snchez etal [2020, J. Chem. Phys., 152, 014304]. The measurements at 279nm and 243nm show signals that are consistent with rapid dissociation along the C–I bond occurring on timescales that are consistent with previous measurements. The measurements at 254nm show a significantly longer excited state lifetime with a secondary feature appearing after 100fs which is indicative of more complex dynamics in the excited state. The time-dependence of the changes are consistent with the previously measured MPI photoelectron spectroscopy measurements of Warne etal, [2019, Phys. Chem. Chem. Phys., 21, 11142]. The consistency of the signal appearance across ionization processes suggests that the extended observation time at 254nm is not an artefact of the previously used MPI process but is caused by more complex dynamics on the excited state potential. Whether this is caused by complex vibrational dynamics on the dominant ³ Q ₀ state or is due to enhanced population and dynamics on the ¹ Q ₁ state remains an open question.

CH ₃ I 在三个紫外泵浦波长（279nm、254nm、243nm）下的解离动力学是在时间分辨光电子能谱实验中使用极紫外探针测量的。结果与之前公布的 269nm 泵浦波长数据进行了比较，[2020, Phys. 化学 化学 物理。, 22 , 25695]，使用多光子电离 (MPI) 探针进行互补光电子能谱实验 [2019, Phys. 化学 化学 物理。, 21 , 11142] 以及最近 Murillo-Snchez等人的动作光谱测量[2020, J. Chem. 物理。, 152, 014304]。279nm 和 243nm 处的测量显示的信号与在与之前测量一致的时间尺度上发生的 C-I 键快速解离一致。254nm 处的测量显示激发态寿命显着延长，100fs 后出现次要特征，这表明激发态的动力学更为复杂。变化的时间依赖性与 Warne等人[2019, Phys. 化学 化学 物理。, 21, 11142]。电离过程中信号出现的一致性表明，在 254nm 处延长的观察时间不是先前使用的 MPI 过程的人工制品，而是由激发态电位上更复杂的动力学引起的。这是由占主导地位的³ Q ₀状态上的复杂振动动力学引起的，还是由于¹ Q ₁状态上的人口和动力学增强引起的，这仍然是一个悬而未决的问题。