Photodissociation dynamics of D2O via the B̃(1A1) electronic state.
Photodissociation dynamics of D2O via the B̃(1A1) electronic state.
复制标题
DOI：
10.1063/1.3555589
复制
发表时间：
2011-03
期刊：
影响因子：
--
通讯作者：
Yuan Cheng;Lina Cheng;Qing Guo;Kaijun Yuan;D. Dai;Xueming Yang
中科院分区：
文献类型：
--
作者：
Yuan Cheng;Lina Cheng;Qing Guo;Kaijun Yuan;D. Dai;Xueming Yang
利用D原子里德堡“标记”飞行时间技术，结合可调谐真空紫外光分解光源，研究了不同光解波长下B-̃((1)A(1))态D(2)O的光解动力学.测量了平行极化和垂直极化下D(2)O光解产物的TOF光谱。由这些TOF谱得到了产物的动能分布和角分布。由这些分布，得到了OD积的内态分布以及OD量子态特定的角各向异性参数。在B̃((1)A(1))态光解离中观察到两个受不同解离动力学支配的产物通道：基态自由基产物OD(X(2)Π)+D和激发电子态OD(A(2)Σ(+))+D。OD(A)+D通道在B̃((1)A(1))态面上通过绝热路径进行，在OD(A)产物中产生振动激发，而OD(X)+D通道主要是通过B̃((1)A(1))和X̃((1)A(1))态面之间的锥形相交途径产生的。在接近能量极限(v=0时，N∼为50)的转动激发下，由于锥形交叉点产生的角力很大，OD(X)积非常热。然而，在振动态v=0的占优势布居的OD(X)产物中，振动激发是冷的。在不同光解波长下的详细实验结果表明，在较高能量下，B-̃态上开始解离的不稳定周期轨道具有较强的OD内态激发程度。OD(A)产物的负角各向异性参数表明，从这些周期轨道出发的绝热解离路径中的角力改变了B̃((1)A(1))←X̃((1)A(1))平行跃迁激发的D(2)O分子的原始角分布。
Photodissociation dynamics of D(2)O in the B̃((1)A(1)) state at different photolysis wavelengths have been investigated using the D-atom Rydberg "tagging" time-of-flight (TOF) technique, in combination with a tunable vacuum ultraviolet photolysis light source. TOF spectra of the D-atom product from the D(2)O photodissociation in both parallel and perpendicular polarizations have been measured. Product kinetic energy distributions and angular distributions have been derived from these TOF spectra. From these distributions, internal state distributions of the OD product as well as the OD quantum state specific angular anisotropy parameters have been derived. Two product channels governed by distinct dissociation dynamics have been clearly observed in the B̃((1)A(1)) state photodissociation: ground electronic state radical product OD(X (2)Π) + D and excited electronic state OD(A (2)Σ(+)) + D. The OD(A) + D channel proceeds via adiabatic pathway on the B̃((1)A(1)) state surface, producing rovibrational excitation in the OD(A) product, while the OD(X) + D channel is generated through nonadiabatic pathway mainly via conical intersections between the B̃((1)A(1)) and the X̃((1)A(1)) state surfaces. Due to strong angular force induced by the conical intersections, the OD(X) product is extremely hot in the rotational excitation close to the energy limit (N ∼ 50 for v = 0). However, the vibrational excitation is cold in the OD(X) product with dominant population in the ground vibrational state v = 0. Detailed experimental results at different photolysis wavelengths show that at higher energy the unstable periodic orbit, from which dissociation starts, on the B̃ state has stronger excitation degree of the OD internal state. The negative angular anisotropy parameters of the OD(A) products suggest that the angular forces in this adiabatic dissociation pathway from these periodic orbits have changed the original angular distribution of the D(2)O molecule excited by the B̃((1)A(1))←X̃((1)A(1)) parallel transition.