اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدQuantum Control of Photodissociation via Manipulation of Bond Softening
166
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present a method to control photodissociation by manipulating the bond softening mechanism occurring in strong shaped laser fields, by varying the chirp sign and magnitude of an ultra-short laser pulse. Manipulation of bond-softening is experimentally demonstrated for strong field (795 nm, 10^12 - 10^13 W/cm^2) photodissociation of H2+, exhibiting substantial increase of dissociation by positively chirped pulses with respect to both negatively chirped and transform limited pulses. The measured kinetic energy release and angular distributions are used to quantify the degree of control of dissociation. The control mechanism is attributed to the interplay of dynamic alignment and chirped light induced potential curves.
قيم البحث
اقرأ أيضاً
A dielectric materials response to light is macroscopically described by electric displacement fields due to polarization and susceptibility, but the atomistic origin is light-cycle-driven motion of electron densities in the restoring forces of the a
tomic environment. Here we report how the macroscopic nonlinear-optical response of a heteronuclear crystal relates to the alignment and orientation of its chemical bonds. Substantial nonlinear emission is only observed if the electric field of an optical single-cycle pulse points from the less electronegative to the more electronegative element and not vice versa. This asymmetry is a consequence of the unbalanced real-space motion of valence charges along the direction of the bonds. These results connect a materials chemical structure to the optical response and may facilitate the comprehension and design of novel materials for applications in optics and lasers on basis of the atoms and how they connect.
Ultrashort electron pulses are crucial for time-resolved electron diffraction and microscopy of fundamental light-matter interaction. In this work, we study experimentally and theoretically the generation and characterization of attosecond electron p
ulses by optical-field-driven compression and streaking at dielectric or absorbing interaction elements. The achievable acceleration and deflection gradient depends on the laser-electron angle, the lasers electric and magnetic field directions and the foil orientation. Electric and magnetic fields have similar contributions to the final effect and both need to be considered. Experiments and theory agree well and reveal the optimum conditions for highly efficient, velocity-matched electron-field interactions in longitudinal or transverse direction. We find that metallic membranes are optimum for light-electron control at mid-infrared or terahertz wavelengths, but dielectric membranes are excel in the visible/near-infrared regimes and are therefore ideal for the formation of attosecond electron pulses.
High-harmonic generation in two-colour ($omega-2omega$) counter-rotating circularly polarised laser fields opens the path to generate isolated attosecond pulses and attosecond pulse trains with controlled ellipticity. The generated harmonics have alt
ernating helicity, and the ellipticity of the generated attosecond pulse depends sensitively on the relative intensities of two adjacent, counter-rotating harmonic lines. For the $s$-type ground state, such as in Helium, the successive harmonics have nearly equal amplitude, yielding isolated attosecond pulses and attosecond pulse trains with linear polarisation, rotated by 120$^{{circ}}$ from pulse to pulse. In this work, we suggest a solution to overcome the limitation associated with the $s$-type ground state. It is based on modifying the three propensity rules associated with the three steps of the harmonic generation process: ionisation, propagation, and recombination. We control the first step by seeding high harmonic generation with XUV light tuned well below the ionisation threshold, which generates virtual excitations with the angular momentum co-rotating with the $omega$-field. We control the propagation step by increasing the intensity of the $omega$-field relative to the $2omega$-field, further enhancing the chance of the $omega$-field being absorbed versus the $2omega$-field, thus favouring the emission co-rotating with the seed and the $omega-$field. We demonstrate our proposed control scheme using Helium atom as a target and solving time-dependent Schr{o}dinger equation in two and three-dimensions.
We present a numerical study of the resonant high harmonic generation by tin ions in an elliptically-polarised laser field along with a simple analytical model revealing the mechanism and main features of this process. We show that the yield of the r
esonant harmonics behaves anomalously with the fundamental field ellipticity, namely the drop of the resonant harmonic intensity with the fundamental ellipticity is much slower than for high harmonics generated through the nonresonant mechanism. Moreover, we study the polarisation properties of high harmonics generated in elliptically-polarised field and show that the ellipticity of harmonics near the resonance is significantly higher than for ones far off the resonance. This introduces a prospective way to create a source of the quasi-monochromatic coherent XUV with controllable ellipticity potentially up to circular.
Photodissociation of a molecule produces a spatial distribution of photofragments determined by the molecular structure and the characteristics of the dissociating light. Performing this basic chemical reaction at ultracold temperatures allows its qu
antum mechanical features to dominate. In this regime, weak applied fields can be used to control the reaction. Here, we photodissociate ultracold diatomic strontium in magnetic fields below 10 G and observe striking changes in photofragment angular distributions. The observations are in excellent qualitative agreement with a multichannel quantum chemistry model that includes nonadiabatic effects and predicts strong mixing of partial waves in the photofragment energy continuum. The experiment is enabled by precise quantum-state control of the molecules.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
