Two-Pulse Field-Free Orientation Reveals Anisotropy of Molecular Shape Resonance
Abstract
We report the observation of macroscopic field-free orientation, i.e., more than 73% of CO molecules pointing in the same direction. This is achieved through an all-optical scheme operating at high particle densities (>1017 cm-3) that combines one-color (ω) and two-color (ω+2ω) nonresonant femtosecond laser pulses. We show that the achieved orientation solely relies on the hyperpolarizability interaction as opposed to an ionization-depletion mechanism, thus, opening a wide range of applications. The achieved strong orientation enables us to reveal the molecular-frame anisotropies of the photorecombination amplitudes and phases caused by a shape resonance. The resonance appears as a local maximum in the even-harmonic emission around 28 eV. In contrast, the odd-harmonic emission is suppressed in this spectral region through the combined effects of an asymmetric photorecombination phase and a subcycle Stark effect, generic for polar molecules, that we experimentally identify.
- Publication:
-
Physical Review Letters
- Pub Date:
- July 2014
- DOI:
- 10.1103/PhysRevLett.113.023001
- arXiv:
- arXiv:1311.3923
- Bibcode:
- 2014PhRvL.113b3001K
- Keywords:
-
- 33.20.Xx;
- 37.10.Vz;
- 42.50.Hz;
- 42.65.Ky;
- Spectra induced by strong-field or attosecond laser irradiation;
- Mechanical effects of light on atoms molecules and ions;
- Strong-field excitation of optical transitions in quantum systems;
- multiphoton processes;
- dynamic Stark shift;
- Frequency conversion;
- harmonic generation including higher-order harmonic generation;
- Physics - Chemical Physics;
- Physics - Atomic Physics;
- Physics - Optics
- E-Print:
- Phys. Rev. Lett. 113, 023001 (2014)