Asymmetric Dissociative Tunneling Ionization of Tetrafluoromethane in ω − 2ω Intense Laser Fields

Abstract

Dissociative ionization of tetrafluoromethane (CF4) in linearly polarized ω-2ω ultrashort intense laser fields (1.4 × 1014 W/cm2, 800 and 400 nm) has been investigated by three-dimensional momentum ion imaging. The spatial distribution of CF3+ produced by CF4 → CF3+ + F + e− exhibited a clear asymmetry with respect to the laser polarization direction. The degree of the asymmetry varies by the relative phase of the ω and 2ω laser fields, showing that 1) the breaking of the four equivalent C-F bonds can be manipulated by the laser pulse shape and 2) the C-F bond directed along the larger amplitude side of the ω-2ω electric fields tends to be broken. Weak-field asymptotic theory (WFAT) shows that the tunneling ionization from the 4t2 second highest-occupied molecular orbital (HOMO-1) surpasses that from the 1t1 HOMO. This predicts the enhancement of the tunneling ionization with electric fields pointing from F to C, in the direction opposite to that observed for the asymmetric fragment ejection. Possible mechanisms involved in the asymmetric dissociative ionization, such as post-ionization interactions, are discussed.

Helicity-dependent dissociative tunneling ionization of CF4 in multicycle circularly polarized intense laser fields

“…56 The obtained structure factors are shown in ref. 18. The three 1t 1 HOMOs have nodes along the C–F axis, which should be translated to minima in the orientation dependent tunneling ionization rate.…”

“…Among others, control of directional ejection of fragment ions with o-2o two-color laser fields has been demonstrated with a variety of molecules. [10][11][12][13][14][15][16][17][18] This includes the application to symmetric molecules such as CO 2 , where the selective breaking of the two equivalent C-O bonds was observed in the Coulomb explosion of CO 2 2+ -CO + + O + 14,15 by deformation of the potential energy surfaces of CO 2…”

Post-Ionization Dynamics of the Polar Molecule OCS in Asymmetric Laser Fields

“…Carrier-envelope-phase (CEP) stabilized few-cycle laser fields and phase-locked two-color laser fields are widely used to investigate the underlying mechanisms of such reaction control (Alnaser and Litvinyuk, 2017). Control of the fragment ejection direction has been demonstrated for a wide range of non-polar (symmetric) molecules, from the simplest diatomic molecule H 2 (D 2 ) (Kling et al, 2006;Roudnev and Esry, 2007;Ray et al, 2009;Znakovskaya et al, 2012;Wanie et al, 2016), summarized in (Ibrahim et al, 2018), to poly-atomic hydrocarbons (Xie et al, 2012(Xie et al, , 2014Alnaser et al, 2014;Miura et al, 2014;Song et al, 2015;Doblhoff-Dier et al, 2016), the triatomic CO 2 molecule (Endo et al, 2016(Endo et al, , 2017, as well as CF 4 as part of this special issue (Hasegawa et al, 2022). Several mechanisms have been proposed such as the interference of dissociation pathways for H + 2 and D + 2 (Kling et al, 2006;Roudnev and Esry, 2007;Ray et al, 2009;Znakovskaya et al, 2012;Wanie et al, 2016;Ibrahim et al, 2018), coherent superposition of vibrational states and electron recollisional excitation for C 2 H + 2 (Alnaser et al, 2014;Xie et al, 2014;Song et al, 2015;Doblhoff-Dier et al, 2016), laser induced bond-weakening for C 2 D + 2 (Miura et al, 2014), or potential deformation for CO 2+ 2 (Sato et al, 2003;Endo et al, 2016Endo et al, , 2017.…”

Dissociative ionization and Coulomb explosion of CH4 in two-color asymmetric intense laser fields

“…The detected ions may pulse generator and an ion coincidence momentum imaging system equipped with a delay-line anode position sensitive detector. 25 The output from a Ti:Sapphire regenerative laser amplifier is introduced to a b-BBO crystal (type-I). The time delay between the fundamental (o) and the second harmonic (2o) pulse was compensated by two birefringent a-BBO crystals.…”

“…It was shown that the asymmetric ejection of the CF 3 + fragment shows a phase shift of Bp with respect to the prediction by the tunneling ionization from HOMO (1t 1 ) and HOMOÀ1 (4t 2 ). 25 The coupling between the two lowest electronic states 26 is suggested as a possible origin of the discrepancy, indicating the importance of postionization effect in ultrafast dissociative ionization associated with the energy difference close to the photon energy. In this study, another tetrahedral molecule, CH 4 , is investigated.…”