RU212813U1 - DEVICE FOR PRODUCING FULLERENE MOLECULES WITH CONTROLLED PARAMETERS IN THE GAS PHASE IN EXCITED ELECTRONIC VIBRATIONAL STATES - Google Patents

Abstract

The utility model relates to tools for the analysis of fullerenes. A device for obtaining fullerene molecules in the gas phase with controlled parameters in excited electronic-vibrational states includes a vacuum chamber 2, in which two electrodes 3 and 4 are placed, configured to communicate with a high-frequency (HF) generator 5 and a system for puffing inert gas 7 between specified electrodes. In the vacuum chamber 2 there is an evaporator 6, the body of which serves as an electrode 3, and the electrode 4 is a metal plate located above it. Electrodes 3 and 4 are made with the possibility of connection to an RF generator 5. The technical result is the production of vapors of excited, indestructible fullerene molecules in the gas phase with controlled parameters: concentration and emission spectra. 1 ill.

Description

The utility model relates to means for obtaining emission spectra of electronic-vibrational states of fullerene vapors.

Luminescent methods of analysis are based on measuring the intensity of the luminescence of a substance when molecules are excited by an external energy source. The physical meaning of the phenomenon of luminescence is the emission of excess energy in the form of converted radiation by excited molecules of matter.

During the transition of the system from state n to state j, the energy of the system changes by ΔE _jn =E _j -E _n . This energy is either absorbed or emitted by the external field. For an electromagnetic field with frequency co, the energy is given by Planck's formula: E=hω. For the most probable processes in non-intense electromagnetic fields, the transition of a quantum system from state n to state j occurs with absorption or emission: E _j -E _n =hω _jn . Thus, the absorbed or emitted radiation has a frequency ω _jn that makes it possible to find the energy difference ΔE _jn of the states of the system. This is the basis of spectroscopic methods for studying molecules. In addition to the spectrum, luminescence is characterized by an intensity that is determined by the excitation energy and depends on the excitation wavelength and concentration of molecules.

To obtain information about the molecule itself, it is best to study the spectra in a rarefied gas. The most effective methods for excitation of gaseous media are gas-discharge methods, for example, an RF discharge.

In an oscillating electric field, an electron oscillates. In inelastic collisions with the molecules of a substance, the internal state of the molecules changes. They can go into an excited state (to a higher level of the discrete spectrum), as well as ionize (go into a continuous spectrum state).

From patent US5620512, published 04/15/1997, a device for the production of diamond films is known. The device contains a vacuum chamber, an evaporator for creating vapors of fullerene molecules in the gas phase, an inert gas inlet system, a microwave generator for excitation of fullerene molecules with a frequency of 2.45 GHz, an output power of 500-1200 W, a spectrometer. The device makes it possible to obtain a diamond film on a substrate by deposition of fullerene molecules as a result of dissociation. The emission spectra of C ₆₀ fullerene molecules and fullerene molecules with an inert gas argon C ₆₀ -Ar are also given, however, the latter represent an emission spectrum of carbon, which indicates the dissociation of fullerene molecules as a result of too much energy being imparted. The disadvantage of the device is the use of a powerful source of excitation, which leads to the dissociation of fullerene molecules, not allowing to keep the molecule intact.

There are currently data on measured absorption spectra as well as theoretical data on the emission spectra of fullerenes in the gas phase, J. Tamuliene, Fullerenes, Nanotubes and Carbon Nanostructures (2015), 23:3, 187-195.

The study of the emission spectra of fullerenes by laboratory methods was carried out in the work of A.A., Vostrikov, D.Yu. Dubova, A.A. Agarkova, JETP Letters (1996), vol. 63, no. 12, pp. 915-919 "Electron-induced emission of C ₆₀ fullerene in the gas phase" using a pulsed electron beam to excite the emission spectra of the electronic-vibrational states of fullerene molecules in the gas phase. However, these attempts were unsuccessful, probably due to the influence of thermal relaxation processes of these states. This determines the relevance of solving the scientific and technical problem associated with obtaining by instrumental methods the emission spectra of the electronic-vibrational states of fullerene vapors.

From patent RU2427667, published 08/27/2011, a device is known for determining the thermal vacuum deposition of alloys by emission spectroscopy. The device contains a vacuum chamber, in which two electrodes are placed, to which an RF generator is connected, an evaporator for creating vapors of the evaporated alloy, a spectrometer, and a personal computer. The device makes it possible to calculate the deposition rate of the evaporated alloy from the registered emission spectra as a result of excitation of the evaporated alloy by an RF discharge. The disadvantage of this device is that it does not allow you to create and control the parameters of fullerene molecules in the gas phase.

The closest technical solution to the claimed device is a device for obtaining fullerenes known from patent US5876684, published on 03/02/1999.

The technical result of the proposed utility model is to obtain in a wide range of vapor concentrations of undestroyed excited fullerene molecules in the gas phase with controlled parameters, which include the concentration and emission spectra of the electronic-vibrational states of fullerene molecules in the gas phase.

Achieving this goal is possible using a device for obtaining fullerene molecules in the gas phase with controlled parameters in excited electronic-vibrational states, including a vacuum chamber in which two electrodes are placed, configured to communicate with a high-frequency (HF) generator and an inert gas puffing system.

The difference of the device lies in the fact that an evaporator is placed in the vacuum chamber, the body of which serves as one of the electrodes, and the other electrode is a metal plate located above the evaporator, while the electrodes are made with the possibility of connecting to the RF generator and letting the inert gas of the corresponding system between them. Preferably, the frequency of the RF generator is 13.56 MHz, and its output power is in the range from 30 to 600 watts.

Preferably, the frequency of the RF generator is 13.56 MHz, and its output power is in the range from 30 to 600 watts.

Preferably the spectrum is recorded in the range from 200 to 1100 nm.

Preferably, the evaporator housing is made of metal, and one of the electrodes is the evaporator housing, and the other electrode is a metal plate located above the evaporator.

Preferably the evaporator has a temperature controlled in the range from 550 to 800°C.

Preferably, the device contains a controller for determining the concentration of fullerene molecules based on the measurement of the heating temperature of the evaporator.

The essence of the utility model is illustrated by drawings, in which:

Fig. 1 - diagram of a device for measuring the electronic-vibrational states of fullerene molecules,

Fig. 2 - graph of the dependence of the concentration of fullerenes on the heating temperature of the evaporator

The device schematically shown in Fig. 1, contains a spectrometer 1 and a vacuum chamber 2. Two electrodes 3, 4 are placed in the vacuum chamber, to which an RF generator 5 is connected, designed to create an RF discharge between electrodes 3, 4. An evaporator 6 is placed in the vacuum chamber to create fullerene vapors in the discharge gap between the electrodes 3,4. The device also contains a system 7 for puffing inert gas between the electrodes 3, 4 to ensure the ignition of a homogeneous RF discharge between them. In this case, the spectrometer 1 is equipped with a spectrum processing unit with the function of subtracting the reference spectrum of an inert gas.

The RF generator 5 is characterized by an output power of 30-600 W and a frequency of 13.56 MHz.

The spectrometer is designed to record spectra in the range from 200 to 1100 nm.

The body of the evaporator 6 is at least partially made of metal. The body or part of the evaporator 6 serves as an electrode 3. The other electrode 4 is made in the form of a metal plate located above the evaporator 6.

The evaporator has a temperature controlled in the range from 550 to 800°C to obtain fullerene vapors of various concentrations from the substance loaded into the evaporator, for example, a fullerene precursor, depending on the temperature of the evaporator.

The device also contains a pressure sensor 8 and a controller 9, with a thermocouple 10 integrated with it, designed to determine the parameters of the vapors between the electrodes 3, 4, in particular, to determine the concentration of fullerene molecules based on the measurement of the temperature of the evaporator 6. The device also includes a converging lens 11 to collect the discharge gap radiation and transfer it to the fiber-optic cable connector, as well as a personal computer, PC, 12, which includes a spectrum processing unit.

The RF generator 5 is characterized by an output power of 30-600 W and a frequency of 13.56 MHz. The specified power range and frequency of the RF discharge provide enough energy to excite fullerene molecules while maintaining the integrity of the molecules.

The device allows recording spectra in the range from 200 to 1100 nm. In this case, the spectrum has a typical form of bands of electronic transitions of fullerene molecules, including vibrational-rotational transitions. The luminescence spectrum of fullerenes is recorded by a high-resolution spectrometer 1 with a symmetric crossed Czerny-Turner optical scheme, which makes it possible to obtain a resolution of up to 0.02 nm. For radiation outputs, vacuum chamber 2 is equipped with an optical window made of KU-1 material, which provides transmission from 180 nm, behind which is located a converging lens 11, also made of KU-1 material, with a focal length of 20 cm, which makes it possible to focus the radiation of the discharge gap on the input fiber - optical cable. Light from the fiber-optic cable enters the spectrometer through the optical connector, after which it enters the spectrometer's input slit installed in the optical connector.

The evaporator 6 is made of metal, for example, from molybdenum, since molybdenum has a low coefficient of linear expansion, which allows it to retain its shape at high temperatures, and molybdenum is refractory, which prevents the spread of molybdenum ions into the discharge. The metal plate 4 acts as the active electrode, and the evaporator 6 or its part near the vapor outlet acts as the passive electrode 3. The potential drop between the RF discharge plasma and electrodes 3, 4 depends on the ratio of their areas; in this case, the potential drop in the discharge is concentrated to a greater extent at the active electrode 4, which makes it possible to realize higher electron energies and also lead to intense ionization processes. The location of the electrode 4 above the evaporator 6 ensures the formation of an RF discharge in the path of the fullerene flow.

Evaporator 6 made with the possibility of heating it to a temperature in the range of 550-800°C to ensure the relative concentration of fullerenes in the total volume at the level of 0.1-10% at a pressure of 10 Torr.

On FIG. Figure 2 shows a plot of fullerene concentration versus evaporator heating temperature.

At a temperature of 550°C the concentration of fullerenes is 10 ¹⁴ cm ^-3 , at a pressure of 10 Torr=3.54⋅10 ¹⁷ cm ^-3 , the relative concentration is 0.1%, at a temperature of 800°C the concentration of fullerenes is 1016, the relative concentration is 10 %.

The implementation of the device in the proposed form makes it possible to obtain, in a wide range of concentrations, pairs of indestructible excited fullerene molecules in the gas phase with controlled parameters, which include the concentration and emission spectra of the electronic-vibrational states of fullerene molecules in the gas phase.

The device works as follows. The evaporated substance, which is a precursor of fullerenes or a powder of C ₆₀ fullerene molecules, is placed in the evaporator 6 located in the vacuum chamber 2, which is made with the possibility of heating it to a temperature in the range of 550-800°C, which makes it possible to change the state of aggregation of the evaporated substance, partially converting it into pairs of fullerenes. The vacuum chamber 2 is evacuated, while the pressure sensor 8 controls the degree of vacuum. To create a homogeneous RF discharge, an inert gas, for example, krypton, is supplied to the vacuum chamber 2 using an inert gas puffing system 7, while two mechanisms of excitation of the electronic levels of the C ₆₀ molecule are possible: by electrons and by transferring the excitation energy of inert gas atoms to fullerene molecules. The RF generator 5 is turned on with a characteristic output power of 30-600 W and a frequency of 13.56 MHz. The reference spectra of an inert gas are recorded by spectrometer 1. With the help of a rotary device (not shown), evaporator 6 is opened, as a result of which fullerene vapors enter the discharge gap with a distance between the electrodes of 27 mm. up to 800°С in the evaporator, 4 g of fullerenes are evaporated. The concentration of the fullerene vapor flow is determined by the controller 9 by the measured heating temperature of the evaporator 6, which is controlled in the range of 550-800°C. Using spectrometer 1, the luminescence spectra of a mixture of fullerene molecules and an inert gas excited by an RF discharge are recorded, from which the reference spectrum of an inert gas is subtracted using PC 12. RF generator 5 is turned off.

The emission spectra of the electronic-vibrational states of fullerene vapors recorded at various vapor concentrations are displayed on the screen and stored on a personal computer 12.

Claims (1)

A device for obtaining fullerene molecules in the gas phase with controlled parameters in excited electronic-vibrational states, including a vacuum chamber in which two electrodes are placed, configured to communicate with a high-frequency (HF) generator and an inert gas puffing system, characterized in that in a vacuum The chamber contains an evaporator, the body of which serves as one of the electrodes, and the other electrode is a metal plate located above the evaporator, while the electrodes are made with the possibility of connecting to the RF generator and letting the inert gas of the corresponding system between them.

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