激光场和温度对氢氰酸分子准直的影响

Influences of laser field and temperature on molecular alignment of hydrogen cyanide molecule

通过分裂算符方法求解氢氰酸(HCN)分子的核转动波包,研究了激光场脉冲宽度、载波频率、激光峰值强度以及转动温度等参数对HCN分子准直程度的影响.结果表明,在温度T=10 K,使用脉冲宽度为100 fs,波长为800 nm,激光峰值强度I<4×10^(13)W/cm^2范围内的激光场准直HCN分子时,最高准直度随光强增加升高,并且随光强增加,最高准直度增速变缓.在温度T=10 K,准直激光脉冲宽度为100 fs,波长为800 nm,峰值强度I=2×10^(13)W/cm2时,随激光载波频率在0.38×10^(15)Hz<v<1.13×10^(15)Hz范围内增加,HCN分子最高准直度出现振荡,在载波频率v=(0.4+0.1·n)×10^(15)Hz(n=1,2,3)时,最高准直度取极大值.在准直激光脉冲宽度为100 fs,波长为800 nm,峰值强度I=2×10^(13)W/cm2时,随温度在0 K<T<90 K范围内上升,准直度明显下降.

The nuclear wave packet evolution of hydrogen cyanide molecule is traced analytically with the split operator method. Influence on alignment of pulse duration, carrier frequency, intensity of femtosecond laser pulses and rotational temperature was studied. The calculations demonstrate that if the molecule nuclear wave packet is created by one 100 fs, 800 nm laser pulse at intensity of I﹤4×10^13 W/cm^2 at a temperature of T=10 K, the global maximum value of alignment parameter within time period longer than revival period increases with laser intensity, meanwhile the acceleration of maximum alignment decreases with laser intensity. If the wave packet is created by one 100 fs, 800 nm laser pulse at an intensity of I=4×10^13 W/cm^2 at temperature T=10 K,the maximum alignment oscillates with the laser carrier frequency in the range of 0.38×10^15 Hz〈ν〈1.13×10^15 Hz and comes up to a local maximum value at a carrier frequency of ν=（0.4＋0.1·n）×10^15 H. If the wave packet is created by one 100 fs, 800 nm laser pulse at an intensity of I=2×10^13 W/cm^2 at temperature 0 K﹤T﹤90 K, the degree of alignment decreases obviously with temperature in the range of and slowly deceases to arrive at an asymptotic value.