Selective Ionization of Oriented Nonpolar Molecules with Asymmetric Structure by Phase-Controlled Two-Color Laser Fields

Abstract

We report on the selective ionization of oriented nonpolar molecules with asymmetric structure by using phase-controlled two-color omega + 2omega laser pulses with an intensity of 1.0 x 10(13) W/cm(2) (tunneling ionization regime) and a pulse duration of 130 fs. The orientation of 1-bromo-2-chloroethane was monitored by the directional asymmetries of the forward-backward emission in dissociative ionization. The observed direction of orientation clearly confirms that molecular orientation is induced not by dynamic orientation but by selective ionization of oriented molecules, which reflects the structure of the highest occupied molecular orbital. This method can be applied for the vast majority of molecules.

Probing the tunnelling site of electrons in strong field enhanced ionization of molecules

“…Equal flux of any charge state to both sides is observed. Second, if the symmetry of the electric field is broken either by using a carrier-envelope phase locked fewcycle pulse 16,17 or a two-colour pulse [12][13][14][15]18 , then the asymmetric laser field can potentially redistribute the remaining electrons in the left behind molecular ion. This is a highly interesting phenomenon in itself.…”

Molecular tunnelling ionization of allyl halides induced by phase-controlled two-colour laser fields

“…We have reported that the mechanism of the OMS-TI induced by phase-controlled ω + 2ω laser fields can be explained by the geometric structure of the HOMO [26,[29][30][31][32][33]; thus some kind of screening due to multi-electron effects that cancel the Stark shift could be induced. A comprehensive theory involving multielectron effects for any molecule is now in progress, and the experimental results of OSM-TI for C 3 H 5 Cl and C 3 H 5 Br with intermediate conditions will be a benchmark for the developed theory of molecular TI.…”

“…As a result, the asymmetric waveform of an LP ω + 2ω laser field can selectively ionize molecules while discriminating the headtail order of molecules with asymmetric structure. We have experimentally demonstrated that OSM-TI is induced as a consequence of the directionally asymmetric TI of molecules with an asymmetric HOMO [26,[29][30][31][32][33].…”

“…We have experimentally investigated orientation-selective molecular TI (OSM-TI) induced by LP ω + 2ω fields for various molecules [26,[29][30][31][32][33]. The method is capable of discriminating the head-tail order of the molecules, which is generally difficult to achieve by single-frequency laser fields.…”

Ultrashort polarization-tailored bichromatic fields from a CEP-stable white light supercontinuum

“…Ultrashort bichromatic laser fields have emerged as a new twist to coherently control ultrafast electron dynamics in atoms [1][2][3][4][5][6], molecules [7][8][9] and solids [10][11][12]. In recent years, (ω : 2ω)-fields have been employed in numerous applications to observe and manipulate the motion of electron wave packets on their intrinsic timescales.…”