Similarities and differences between molecular spectra, atomic spectra and molecular spectra of mole

Atomic spectroscopy and molecular spectroscopy are both two types of spectral juxtaposition, but there are also essential differences, the specific differences are as follows.

The spectrum of both atoms and molecules is the result of transitions between the energy levels of internal motion. None of them contribute to the spectrum. Because the external motion of the molecule is only translational, that is, the translational motion of the molecule as a whole, and the external motion of the atom is only the translational motion of the atom as a whole, the energy level difference between the translational kinetic energy levels is very small, and the wavelength of the transition is extremely long, which is not within the scope of ordinary spectral measurement.

The difference between atomic and molecular spectra.

1. The way of generation is different.

The atomic spectrum is a spectrum composed of a series of wavelengths of light emitted or absorbed by the electrons in the atom when the energy changes, and the transition between energy levels, and the absorption spectrum stripes can correspond to the emission spectrum one-to-one. The spectrum of each atom is different.

Molecular spectroscopy refers to the absorption or emission spectrum of a molecule when it changes from one energy state to another, which is mainly generated by the rotation of the molecule around the axis, the vibration of the atoms in the molecule in the equilibrium position, and the transition of electrons within the molecule.

2. The two have different functions.

Molecular spectroscopy is the main way to provide internal information of molecules, and many properties such as moment of inertia, bond length and bond strength of molecules, and molecular dissociation energy can be determined according to molecular spectra, so that the structure of molecules can be inferred. Now, the results of molecular spectroscopy are of great importance for astrophysics, plasma and laser physics.

Atomic spectroscopy provides a wealth of information about the internal structure of atoms. Its research plays an important role in the birth and development of the exciter, and will further promote the development of laser technology; In turn, laser technology provides an extremely effective means of spectroscopy. Atomic spectroscopy is also widely used in chemistry, astrophysics, plasma physics, and other applied technical disciplines.

3. The two forms of movement are different.

The internal motion of an atom is only the movement of electrons, so only the transitions between the energy levels of the electrons in it cause the spectrum. The nucleus of an atom is just a point of mass with an electric charge and a magnetic moment, and in the absence of an applied magnetic field, there is no energy level of motion for transition. In conclusion, atomic spectroscopy is relatively simple, just the result of the transition between the electron energy levels in it, i.e., the electron spectrum.

The rotational motion of the atom as a whole has a small moment of inertia, so the energy level difference is very small, so it does not contribute to the spectrum.

There are many internal movements of molecules, such as the rotational motion of the molecule as a whole around its center of gravity, the movement of each bond within the molecule, and the transition between the various electron energy levels in the molecule. This is the so-called rotation, vibration and electronic motion.

Because the electronic transitions in an atom are between electronic states (also electron states), and the separation between the energy levels is large, the spectrum reflects the current spectrum.

The electronic transition in the molecule is not only the transition between the electronic states, but also the vibrational dynamic transition within the energy level of the electronic state, and the rotational dynamic transition within the vibration dynamic, and the energy level interval is very dense, so it is reflected in the spectrum as a banded spectrum.

Molecular spectrum is produced by changes in the energy level, vibration and rotational energy level of electrons in a molecule, which is manifested as a band spectrum.

Examples of such analysis methods include ultraviolet-visible spectrophotometry (UV-VIS), infrared spectroscopy (IR), molecular fluorescence spectroscopy (MFS) and molecular phosphorescent spectroscopy (MPS), nuclear magnetic resonance and paramagnetic resonance spectroscopy (N), etc.

The sample itself is excited and then returns to the ground state, emitting a characteristic spectrum. There is generally no light source in the emission spectrum, and if there is a light source, it is also used for wavelength confirmation. The light source is also definitely turned off at the time of measurement.

There is a light source in the absorption spectrum, and the light source is always the source of the measurement, and the light source, sample, and detector are in a straight line. If not in a straight line, it may be a fluorescence spectrum.

Electrons and photons collide with each other for energy exchange. When the electron momentum is greater than the photon momentum, the emission spectrum is generated; When the momentum of the electron is less than the momentum of the photon, an absorption spectrum is produced.

The electrons absorb energy to make a transition, and there is an energy change in the process, which comes out in the form of light.

In the molecule, the energy of the electronic state is 50 100 times greater than the energy of the vibrodynamic force.

The energy of the vibration dynamic is 50 100 times greater than the energy of the rotational dynamic. Therefore, in the transitions between the electronic states of molecules, there are always vibrational transitions and rotational transitions.

Whereas. Many spectral lines are clustered together. Whereas. Formation.

Molecular spectroscopy. Hence the molecular spectrum.

It is also called a strip spectrum.

In the atom, when the primordial partner somehow goes from the ground state.

When raised to a higher energy state, the energy inside the atom increases, and this excess energy will be emitted in the form of light, thus producing the emission spectrum of the atom, i.e.

Atomic. Grinding the source cause.

For. This atomic energy.

The change of state is discontinuous quantum, and the resulting spectrum is also made up of some discontinuous bright lines, so.

Atomic. Also called.

Linear spectra.