发射和吸收光谱之间的差异

发射与吸收光谱|吸收光谱与发射光谱

Light and other forms of electromagnetic radiations are very useful, and widely used in analytical chemistry. The interaction of radiation and matter is the subject of the science called spectroscopy. Molecules or atoms can absorb energy or release energy. These energies are studied in spectroscopy. There are different spectrophotometers to measure different types of electromagnetic radiations such as IR, UV, visible, X-ray, microwave, radio frequency, etc.

发射光谱

当给出一个示例,我们可以获取信息about the sample depending on its interaction with the radiation. First, the sample is stimulated by applying energy in the form of heat, electrical energy, light, particles, or a chemical reaction. Before applying energy, the molecules in the sample are in a lower energy state, which we call the ground state. After applying external energy, some of the molecules will undergo a transition to a higher energy state called the excited state. This excited state species is unstable; therefore, trying to emit energy and come back to the ground state. This emitted radiation is plotted as a function of frequency or wavelength, and it is then called an emission spectra. Each element emits specific radiation depending on the energy gap between the ground state and the excited state. Therefore, this can be used to identify the chemical species.

吸收光谱

吸收光谱是吸光度与波长的图。除了波长的吸光度外，还可以针对频率或波数绘制。吸收光谱可以是两种类型的原子吸收光谱和分子吸收光谱。当多色紫外线或可见辐射在气相中通过原子时，只有某些频率被原子吸收。吸收的频率有所不同。当记录传输辐射时，光谱由许多非常狭窄的吸收线组成。在原子中，这些吸收光谱被电子过渡视为。在分子中，除了电子过渡之外，还可以进行振动和旋转转变。因此，吸收光谱非常复杂，分子吸收紫外线，IR和可见辐射类型。

吸收光谱与发射光谱之间有什么区别？ •当原子或分子激发时，它会在电磁辐射中吸收一定的能量；因此，在记录的吸收光谱中将不存在该波长。 •当物种从激发态回到基态时，会发出吸收的辐射，并记录下来。这种类型的频谱称为发射光谱。 •简单的术语，吸收光谱记录了材料吸收的波长，而发射光谱记录了材料发出的波长，这些波长曾经被能量刺激。 •与连续的可见光谱相比，发射和吸收光谱都是线光谱，因为它们仅包含某些波长。 •在发射范围内，黑色的背面只有很少的彩色带。但是在吸收光谱中，连续光谱中的暗带很少。吸收光谱中的暗带和同一元素发射光谱中的彩带相似。