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2·1 前言凡温度高于绝对零度的物体都发出辐射,统称为“热辐射”。在这里,我们只探讨3~14微米波长范围内发射的热辐射,原因有二。首先,在这个光谱波长频带范围内,地面温度的物体发射出的大部份能量,都是以物体的电磁场和热激励的振动一旋转电子能级状态之间的能量交换形式发射出来。其次,是因为在这频带内,有透过大气窗,容许在比较长的频率范围内作信号探测。
2.1 INTRODUCTION All objects at temperatures above absolute zero emit radiation, collectively referred to as “thermal radiation.” Here, we only discuss the thermal radiation emitted in the wavelength range of 3 to 14 microns for two reasons. First of all, most of the energy emitted by objects at surface temperature over this spectral wavelength band is emitted as an exchange of energy between the electromagnetic field of the object and the excited-oscillating-spin electron energy state of the object. Secondly, because in this frequency band, there is a window through the atmosphere that allows signal detection over a relatively long range of frequencies.