On the possibility of enhanced multiple ionization near conical intersections

Abstract

Recent measurements of the transient laser-induced fragmentation of photoexcited 1,3-cyclohexadiene undergoing isomerization have seen that some of the fragments have higher velocity at the pump-probe delay corresponding to the time of passage through a conical intersection (Coln). (http://arxiv.org/abs/1212.3728) Here we explore several possible explanations related to the electronic and ionic structure of molecules in the vicinity of Colns and suggest some experimental tests that could illuminate the mechanism and ultimately control this behaviour.

Ultrafast polyene dynamics: the ring opening of 1,3-cyclohexadiene derivatives

“…63 Petrovic et al used enhanced multiphoton ionization to identify the 2A/1A conical intersection. 64,65 Such a rapid decay implies that the lifetime of the 2A state is shorter than the vibrational period of the principle vibration involved. Thus, the internal conversion occurs on the first pass of the wavepacket.…”

Probing ultrafast electronic and molecular dynamics with free-electron lasers

“…More detailed analysis of the fragment distribution patterns in the strong-field case reveals that the delayed transient increase in the energetic fragments is correlated with formation of the dication CHD 2+ [83,85]. This delayed enhancement in the cross section for double ionization occurs during the passage of the molecular geometry through the vicinity of a known conical intersection between the ground and first excited states in the molecule [83,85].…”

“…The same motif appears in important biochemical processes such as vitamin D synthesis. The CHD/HT isomerization has received significant attention in experiments and calculations that seek to investigate the role that the nonBorn-Oppenheimer interactions play in the photorelaxation [24,75,[77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96]. It is now known that the ring opening is complete in less than 200 fs, as a result of nonradiative relaxation through a conical intersection between the S 1 and S 0 states [75,81,84].…”

The three pillars of photo-initiated quantum molecular dynamics

“…The topics under discussion range very broadly, from high resolution spectroscopy, 1,2 to ultrafast dynamics [3][4][5][6][7][8][9] and coherence 10,11 quantum control [12][13][14][15] and strong eld attosecond physics. [16][17][18] Yet underlying this seemingly disparate collection of topics is the unifying theme of light-matter interactions. Why is this an important subject?…”