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questions :Vibration spectrum
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[Visitor (112.21.*.*)]answers [Chinese ]Time :2021-02-02
The vibrational energy of molecules is quantum. If a molecule consists of N atoms, there should be a separate vibrational mode of 3N-6 (3N-5 for line molecules) for non-line molecules. Carbon dioxide, for example, is a line-shaped three-atom molecule that has three different vibrational modes (the second of which is a two-way combination).

Quantumization of each vibration mode can be expressed by a relevant quantum number, if the frequency of vibration is v1, v2、..., then the corresponding vibration quantum number is n1, n2、..., molecule vibration dynamics are generally in order of quantum number (n1, n2、...) to be indicated. If these vibrations are approximately considered to be simple, the allowed energy values can be expressed in the following way:
H in the style is the Pplank constant; c is the speed of light; n1、n2、... Desirable 0, 1, 2、... and a series of integers. Minimum vibration dynamics (v1-0, v2-0、...) The energy is not equal to zero, but has a defined value, which is called zero-point energy. The choice of quantum number v for linear resonator vibration is fixed as: v ±1.

The emission of radiation occurs when the vison jumps from a higher state (v)to a lower state (v"), and the number of waves emitted is given from the following:

For example, carbon dioxide molecules can radiate 10.6 microns of light when they jump from (001) to (100) and 9.6 microns when they jump from (001) to (020). Because there is usually a change between the rotational energy stages in the vibration spectrum, the vibration spectrum is obtained.
The interval between the vibration energy stages in the molecule is about 100 times longer than the rotational energy stage interval, generally 0.05 to lev, corresponding to the photon wavelength is about 1 to 25 m, this spectrum is located in the near-infrared zone and the mid-infrared region, so it is also known as the infrared spectrum, shorthand for IR.

The vibrational leap of the molecule is accompanied by changes in the rotational energy level, so the vibration spectrum of the whole molecule contains several spectral bands, which are actually vibration-rotation spectra, that is, the biatomic molecules usually have vibration and rotation at the same time, the vibration energy state changes with the rotational energy state changes, resulting in the spectrum, its wavelength range is generally located in the infrared region.

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