Laser observations of the ground-state hyperfine structure of sodium and of temperatures in the upper atmosphere
Laser observations of the ground-state hyperfine structure of sodium and of temperatures in the upper atmosphere
复制标题
钠基态超精细结构和高层大气温度的激光观测
作者：
A. J. Gibson;L. Thomas;S. K. Bhattachacharyya
钠的高度分布在大约80和100公里之间，已经由几个小组从调谐激光束的共振散射的观测中测量出来1 -7。此外，通过在激光雷达系统的接收器中加入已知温度的钠电池，对这一高度范围内的温度进行了估计。在所有这些测量中，所用激光器的线宽与钠D1或D2共振线的线宽相当或更大。钠原子的基态能级3s 2S 1/2由两个超精细结构组成，相对于质心分别位于−1.107 GHz和0.664 GHz。由于上能级对应的超精细结构，D1为3 p 2 P1/2，D2为3 p 2 P3/2，D1和D2复合物分别有4个和6个组分。由于十个分量的相对强度和频率是众所周知的，因此可以计算理论线形9。对于高于约6 K的温度，发生这些组分的共混，并且对于低于约456 K的温度，D1和D2络合物的线轮廓显示两个不同的峰。在这封信中，使用可调谐窄带激光器的D2线的轮廓的初步测量，并用于推导的钠层的峰值附近的温度。
The height distributions of sodium between about 80 and 100 km have been measured by several groups from observations of the resonance scattering of a tuned laser beam1–7. Furthermore, estimates of temperatures in this height range have been made4 by incorporating a sodium cell of known temperature in the receiver of the laser radar system. In all these measurements, the linewidths of the lasers employed have been comparable with, or greater than, that of the sodium D1 or D2 resonance line. The ground level of sodium atoms, 3s 2S1/2 consists of two hyperfine-structure components at −1.107 GHz and 0.664 GHz relative to the centroid8. Because of the corresponding hyperfine structure of the upper levels, 3p 2P1/2 for D1 and 3p 2P3/2 for D2, four components contribute to the D1 and six to the D2 complexes. Since the relative strengths and frequencies of the ten components are well known, the theoretical line shape can be computed9. For temperatures above about 6 K, blending of these components occurs and for temperatures below about 456 K the line profiles of both D1 and D2 complexes show two distinct peaks. In this letter preliminary measurements of the profile of the D2 line using a tunable narrow-band laser are presented and used to deduce the temperature near the peak of the sodium layer.