Probing degrees of orientation of top molecules with odd-even high-order harmonics

Abstract

Molecular orientation has wide applications in physics and chemistry. However, the degree of orientation achieved in experiments is difficult to evaluate, especially when three-dimensional (3D) orientation is involved. We show numerically and analytically that odd-even high-harmonic generation (HHG) from asymmetric molecules is sensitive to both the degree of orientation and the molecular structure. Based on the observations, a simple procedure is proposed to probe the degree of orientation with odd-even HHG, without the need of solving the rotational equation. This procedure can be applied to 3D-oriented top molecules such as polar or nonpolar planar ${\mathrm{H}}_{3}{}^{2+}$ with high resolution.