通过奇偶谐波谱标定线性不对称分子的取向度

Calibrating the Degree of Orientation of Linear Asymmetric Molecules with Odd-even Harmonic Spectrum

分子取向在物理和化学中有着广泛的应用,然而,实验上的取向度很难评估。通过求解二维含时薛定谔方程的数值方法,研究了线性不对称分子HeH^(2+)和H_(3)^(2+)的高次谐波产生,展示出线性不对称分子既发射奇次谐波又发射偶次谐波。另外,数值和解析方法模拟表明:不对称分子的奇偶高次谐波产生对取向度和分子结构都很灵敏。基于观测结果,提出了一种简单的方法来探测奇偶谐波的取向度,即利用偶奇率(偶次谐波产量与奇次谐波产量之间的比率)并考虑分子的结构可更精确地探测分子的取向度,且无需求解转动方程;同偶奇率标定的取向度相比,通过新方案标定的取向度更接近于精确的结果,该方案可应用于线性不对称分子HeH2+和H23+的取向度标定。

Molecular orientation has wide applications in physics and chemistry.However,the degree of orientation achieved in experiments is difficult to evaluate.Through solving the two-dimensional time-dependent Schrödinger equation numerically,the high-order harmonic generation from linear asymmetric molecules is studied,which emit both odd and even harmonics.It is showed numerically and analytically that odd-even high-harmonic generation 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.In other words,the degree of molecular orientation can be accurately calibrated by using the even-odd ratio(the ratio between even harmonic yields and odd harmonic yields)and considering the molecular structure,without the need of solving the rotational equation.Compared with the even-odd ratio calibratied results,the calibratied degree of orientation in the new scheme is closer to the exact result.The procedure can be applied to linear asymmetric molecules HeH^(2+)and H_(3)^(2+).