JPH10132740A - Non-contact measuring method for excited state of nitrogen molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact measuring method for the excited state of nitrogen molecules capable of easily and well obtaining information on the vibrational and rotational state of nitrogen molecules to be measured. SOLUTION: The movement of energy caused by the collision of inert gasses in a metastable state such as He and Ne whose life is long, that is, from 0.1 to few seconds for ionizing nitrogen molecules is used to generate the intermediate state of nitrogen molecular ions and to raise this intermediate state to a higher level by laser light. Then, the light emitted at the time of dropping to a lower level is measured with respect to the wavelength of incident laser to obtain information on the vibrational and rotational state of nitrogen molecules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for non-contact measurement of excited states of nitrogen molecules, and more particularly to a nitrogen flow such as a dilute flow in vacuum equipment or a flow in a discharge tube for laser, which is inaccurate or impossible by measurement with a tracer gas. It is useful when applied to diagnosis and measurement related to

[0002]

2. Description of the Related Art In measuring a nitrogen flow, there are used (a) a method using a tracer gas, (b) a method using light emission by an electron beam, and (c) a method using a two-photon process.

[0003] The above (a) is a method of estimating the state of nitrogen from the behavior of a gas in which a gas that easily emits light, such as iodine, is mixed in a nitrogen stream for a tracer.

[0004] (b) shows a method in which an electron beam is injected into a portion to be measured, and information is obtained from an emission spectrum of nitrogen obtained as a result.

[0005] (c) is a method in which a nitrogen molecule is raised to an excited state of a nitrogen molecule ion by using two-photon collision, and emission is measured when the ion falls to a lower level.

[0006]

Among the prior arts described above, the method (a) uses a tracer gas, and the method is established under the assumption that the tracer gas and nitrogen sufficiently collide and are in a thermal equilibrium state. It is. Therefore, it is difficult to accurately predict the vibration and the rotation state of the nitrogen in the case of the lean flow and thermal equilibrium. In addition, since a tracer gas is often used as a reactive gas, it is necessary to pay attention to the chemical reaction.

(B) is inaccurate and cannot be used for in-discharge measurement because the electron beam assumes the cross-sectional area of the interaction between nitrogen molecules and the electron beam density.

(C) is a process in which two photons collide at the same time, and therefore requires a high-power laser.
There is a problem in cost.

SUMMARY OF THE INVENTION In view of the above prior art, an object of the present invention is to provide a method for non-contact measurement of excited states of nitrogen molecules, which can easily and satisfactorily obtain information on vibration and rotation states of nitrogen molecules to be measured. .

[0010]

According to the structure of the present invention, which achieves the above object, the vibration or rotation of a nitrogen molecule to be measured is caused to collide with a metastable state of an electron or a rare gas generated by electric discharge. The intermediate state of the ion is generated, and at the same time, the intermediate state of the nitrogen molecule ion is raised to the upper level by laser light, and the light emitted when falling to the lower level different from the intermediate state is again adjusted to the wavelength of the incident laser. It is characterized by obtaining information on the vibration and rotation state of the original nitrogen molecule from the emission spectrum of this light.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

This embodiment is based on the following principle. (1) In order to perform measurement using a laser having a medium output or less, energy transfer due to collision of a metastable state of a rare gas (He, Ne, or the like) having a long lifetime of 0.1 to several seconds is used for ionizing nitrogen molecules. (2) Excitation of nitrogen molecular ions (N ₂ ⁺ ) is performed using a tunable laser to obtain only the desired emission. (3) Direct measurement of light emission from N ₂ ⁺ (1st negati
ve state). (4) The above (1) and (2) are performed simultaneously, and the emission from the upper level of N ₂ ⁺ is measured while changing the laser wavelength.
As a result, the vibration and rotation level of the nitrogen molecule (N ₂ ) can be accurately obtained without contact from the emission distribution with respect to the laser wavelength.

This embodiment based on the above principle will be described. FIG. 1 shows an example in which Ne is mixed in a nitrogen stream to generate metastable Ne. In this case, Ne is several% to several tens%.
The degree mixed, DC to the point to be measured the particle beam with a higher energy tens V, or make a metastable state of the rare gas by irradiating a pulse, N in collision with N _{2 2} ⁺ intermediate state N ₂ ⁺ (X ² , Σ ⁺ ).

At the same time as this intermediate state generation, N_Two ⁺(X^Two,
Σ⁺) To higher level N_Two ⁺(B^Two, Σ ⁺Transition energy to)
Laser light with a wavelength near the energy
Of the wavelength width (in this embodiment, 1pm)
Incident.

Since the energy level of the intermediate state changes according to the rotational level in the ground state of N ₂ ,
The resonance transition from the intermediate state to the higher level by the laser beam occurs at discrete wavelengths according to the rotational level. If a resonance transition occurs, the lower level N ₂ ⁺ (X ² ,
Σ ⁺ ) also occurs, and light emission is observed from N ₂ ⁺ . The emission spectrum distribution in the case is strong at the resonance transition condition, because it represents the rotation level of the distribution of the original N ₂ molecule, to grasp the state of the N ₂ molecules on the basis of the emission spectrum of the light.

By shifting the wavelength of the incident laser beam by several nm or more, the vibration states of different N ₂ are measured. In this case, the incident laser light may be either a pulse wave or a continuous wave.

When the wavelength of the extra light emission of N ₂ ⁺ due to the particle beam is close to the wavelength of the light to be measured, the particle beam is pulsated and the life of the metastable state of the rare gas is 0.1.
The above method is realized by irradiating a laser beam after the excess light emission of N ₂ ⁺ has been eliminated (several tens of nanoseconds), utilizing the fact that it is で あ 1 sec. Similar results can be obtained by using He instead of Ne.

FIG. 2 shows a method for measuring nitrogen molecules in a carbon dioxide laser discharge tube. As shown in the figure, in a carbon dioxide gas laser, He is mixed in advance for adjusting the discharge, and a metastable state exists due to the discharge. Therefore, by irradiating the laser beam to the nitrogen molecule ionized in the He metastable state, the nitrogen molecule in the state of transferring energy to carbon dioxide gas can be directly measured as in the above-described process.

Thus, the energy transition state from nitrogen to carbon dioxide, which has conventionally been considered important for laser oscillation, but cannot be measured, can be measured directly and without disturbing the flow and the like.

[0020]

As described in detail with the above embodiments, according to the present invention, the flow of nitrogen in a rare gas and the flow in a discharge tube can be controlled by using a metastable state of a rare gas and a laser without using a reactive substance such as iodine. Light can directly monitor the nitrogen flow, molecular vibrations and rotation.

[Brief description of the drawings]

FIG. 1 is an energy transition diagram showing an embodiment of the present invention.

FIG. 2 is an energy transition diagram showing an embodiment when applied to a carbon dioxide laser.

[Explanation of symbols]

N ₂ ⁺ nitrogen molecular ion N ₂ nitrogen molecule N ₂ ⁺ (B ² , Σ ⁺ ) Upper level N ₂ ⁺ (X ² , Σ ⁺ ) Intermediate state N ₂ ⁺ (X ² , Σ ⁺ ) Lower level

Claims (1)

[Claims] 1. An intermediate state of nitrogen molecular ions is generated by colliding a vibration or rotation state of nitrogen molecules to be measured with a metastable state of electrons or a rare gas generated by electric discharge, and simultaneously with the nitrogen molecular ions The intermediate state is raised to a higher level by laser light, and the light emitted when falling again to a lower level different from the intermediate state is measured with respect to the wavelength of the incident laser. From the emission spectrum of this light, the original nitrogen A non-contact measurement method for excited states of nitrogen molecules, wherein information on vibration and rotation states of molecules is obtained.