n-C_3H_7I和i-C_3H_7I在266nm的光解:烷基自由基分支化对C—I解离动力学的影响(英文)

结合共振增强多光子电离(REMPI)方案,利用离子影像技术研究了n-C3H7I和i-C3H7I分子的光解动力学.分析和比较了它们光解过程中所涉及的能量分配和解离态间的非绝热跃迁信息.它们的I(2P3/2)产物通道的内能所占百分比要大于I*(2P1/2)产物通道的.随着烷烃自由基变得更加的分支化,一方面,原子碎片(I和I*)的能量分布明显变宽,暗示了α-碳原子上的烷基具有更复杂的振转模式;另一方面,在266nm光子的泵浦下,尽管两分子3Q0邝X跃迁的谐振强度表现出很小的差别,但是,产生I*碎片的几率明显降低,从n-C3H7I的0.72降到i-C3H7I的0.46.这可以归因于在光解i-C3H7I过程中弯曲振动模式对产生I和I*的贡献要比n-C3H7I光解过程中弯曲振动模式对I和I*的贡献更明显,使得3Q0与1Q1态之间的非绝热跃迁得到增强.此外,n-C3H7I和i-C3H7I的3Q0邝X跃迁并不完全是平行跃迁,对应的跃迁偶极矩与键轴间的夹角分别约为15°和18°.

Photolysis of n-C3H7I and i-C3H7I at 266 nm: Effect of Alkyl Radical Branching on the Dissociation Dynamics of the C-I Bond

Photodissociation dynamics of,n-C3H7I and i-C387I at 266 nm were investigated using an ion imaging technique combined with resonance enhanced multiphoton ionization(REMPI).Information on energy disposal and a nonadiabatic transition between the dissociative electronic states involved in the photodissociation of both molecules were analyzed and compared.The fraction of intemal energyin the I charmel is greater than that in the I* channel for both molecules.As the alkyl group becomes more branched the energy distribution of the atom fragments(I and I*)becomes obviously wider suggesting that the atkyl radical at the α-carbon atom has more compficated models of the rovibration models.On the other hand.the telative oscillator strengths of these molecules that were pumped using 266 nm photons show a small difference in the 3(Q)0←X transition.The probability of yielding an I* fragment decreases markedly from 0.72 for n-C3H7I to 0.46 for i-C3h7I. This is attributed to the greater contribution of the bending modes for I and I* during the photodissociation of i-C3H7I than that of n-C3H7I leading to an enhancement of the nonadiabatic transition between the 3(Q)0←and1(Q)1 states.Additionally,the 3(Q)0←X transition is not a completely parallel transition forboth molecules and the angle between the transition dipole moment and the bond axis is estimatedto be about 15°for n-C3H7I and 18°for i-C3H7I,respectively.