Pulse-length dependence of high-order harmonic generation in dissociating cyclic organic molecules

Abstract

We compare high-order harmonic generation in gas jets of benzene, cyclohexane, and xenon using ϳ800-nm laser pulses of 70 fs and 240 fs duration. The harmonic intensities of the 7th to 15th orders are studied as a function of laser intensity in the range 5ϫ10 13 to 5ϫ10 15 W cm Ϫ2. Using 240-fs pulses, the dependence of the harmonic intensity on the laser intensity of the organic molecules exhibits significant deviations from the behavior of atoms, and shows strong evidence for harmonic generation from molecular fragments as well as the parent molecule. When the pulse duration is reduced to 70 fs, the intensity dependences of the harmonics are similar to those of xenon. This is attributed to the significant reduction in dissociation occurring during the shorter pulse and suggests that high-order harmonic generation in the ultrafast regime will be important in the understanding of molecular electron dynamics in strong fields.

Multielectron effects in high harmonic generation in N2 and benzene: Simulation using a non-adiabatic quantum molecular dynamics approach for laser-molecule interactions

“…This interest stems from the complexity of the electronic structure in molecules together with the experimental ability to control the orientation between the molecules and the laser pulse using a variety of alignment techniques. While initial studies considered multielectron effects in ionization [21][22][23][24][25][26][27][28][29] , recent studies have considered the role of multielectron effects in HHG [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] . Studying HHG as a function of alignment provides us not only with an insight to the role of molecular electronic structure in HHG, but also with a technique for manipulating the strength of the high harmonics emitted.…”

Enhanced high-order-harmonic generation in a carbon ablation plume

“…The use of few-cycle pulses was earlier demonstrated to be an effective strategy when studying HHG from organic molecules [17][18][19] and so this approach was adopted in our work. A very short laser pulse duration minimizes ionization of atoms, molecules, and clusters, as well as reduces the fragmentation of molecules and clusters.…”

Finite-system effects on high-order harmonic generation: From atoms to solids

“…This model predicts a cutoff in harmonic spectra at Ω Max = 3.17U p + I p , where I p is the ionization potential of the atom, U p = F 2 0 /4ω 2 0 is the ponderomotive energy here expressed as a function of the electric field strength, F 0 , and the driving angular frequency of the laser pulse, ω 0 (Atomic units are used throughout unless otherwise is indicated). In molecular systems, molecular-specific effects have been predicted [5] and observed [6] in the HHG spectra, and processes such as molecular fragmentation from electronic excitation and ionization [7,8] influence the HHG signal [9][10][11]. In atomic and molecular systems, additional cutoffs related to correlated two-electron dynamics have also been predicted [12][13][14] but these have very low signal strength.…”