腔衰荡光谱技术测量O_2禁戒跃迁绝对吸收截面

Determination of the Absolute Absorption Cross Section of Oxygen Forbidden Transition by Cavity Ring down Spectroscopy

腔衰荡光谱技术(CRDS)不仅具有较高的测量灵敏度,还可对样品的绝对吸收进行测量。采用连续激光腔衰荡光谱技术,通过测量O2分子三重禁戒跃迁b1∑g+X3∑g-(3,0)带RQ(5)谱线(波数17266.090 cm-1)处,极限真空及不同气压下的衰荡时间,利用逼近法得到空腔寿命为2.9174 ms,由此拟合获得其绝对吸收截面为1.4998(±0.0967)×10-26cm2,与先前的文献估计值一致。由空腔寿命获得的谐振腔高反镜的反射比为99.989(±0.001)%,较通常的测量方法更为精确,该实验条件下的等效吸收程长比几何程长增大了约9090倍。

Cavity ring down spectroscopy （CRDS） not only has high sensitivity, but also can measure the absolute absorption of the sample gas. The decay time of the oxygen molecule at 17266. 090 cm^-1 is recorded at system＇s limiting vacuum and other different pressure of oxygen filled in the cavity. Therefore, the lifetime of the empty cavity is obtained to be 2. 9174 ms by approaching method, and the absolute absorption cross section of ^RQ（5） rovibrational line of the （3,0） band in the triple forbidden transition b^1∑g^＋-X^3∑g^- of O2 is determined to be 1. 4998（±0. 0967）×10^-26 cm^2 , which is in good agreement with previous estimation, by employing continuous wave CRDS. Additionally, the reflectance of the two identical cavity mirrors, obtained by the approached empty cavity lifetime, is determined to be 99. 989 （±0. 001） %, which is more accurate than usual method, and the equivalent absorption length is prolonged by a factor of about 9090 in our experimental condition.