SU1363030A1 - Method of determining absolute concentration of diamond moleculus in highly rarefied vapours - Google Patents

Abstract

This invention relates to spectroscopic elemental analysis methods. The goal is to increase the accuracy and reliability of the determination. The vapors of the test substance are irradiated with a laser beam with a specially formed uniform distribution of radiation. At the same time, the absolute intensity and the degree of polarization of the laser-excited fluorescence are measured. The absorption coefficient is determined by the degree of polarization and the diameter of the laser beam. The concentration of diatomic molecules is determined from the ratio of the fluorescence intensity to the absorption coefficient. (L co a 00

Description

The invention relates to spectroscopic methods for elemental analysis and can be used to determine the concentration of diatomic molecules in highly dispersed pairs.

The purpose of the invention is to show the accuracy and reliability of determining the concentration of diatomic molecules in highly spaced pairs.

Experiments and calculations have established that for a beam with a uniform power distribution, the average time

The concentration of k atomic molecules of potassium is determined. Saturated

T relaxation during the passage of molecules through the beam can be expressed in terms of potassium dips, heated to T 470 K per meter of beam d, as t 0.5855d-m / 2kT, where T is the vapor temperature j m is the mass of the molecules under study; k is the Boltzmann constant. Measurement of the degree of polarization of a glass fluorescence cell pumped to a pressure not worse than 10 torr is irradiated with linearly polarized radiation of helium-neonon

Fluorescence measurements with a laser laser of the LG-38 type with a power near the excitation makes it possible to determine without-50 mW at a wavelength of 632.8 nm. La is the dimensional parameter of the optical pumping. Studies performed. The indicative beam is expanded three times with the help of a diffusing lens with a focal length of 0.9 meters. When the collisional part of the beam can be neglected, 25 diaphragm parts of the beam are diarrhea processes, the optical distribution parameter d 4 mm - which pumping is equal to the product of the power € € power factor in this case within

of the absorption coefficient B (B is the Einstein coefficient; p is the power density of the exciting radiation) for the average time f of the molecules under study through the laser beam. Consequently, the simultaneous determination of the mean time t of the span (from the diameter of the specially formed uniform laser beam in the circular cross section) and the dimensionless parameter x (from the measured value of the degree of polarization of fluorescence) allows us to calculate the absorption coefficient as BP x / s, with an accuracy in which the error in determining the concentration of molecules will be mainly determined by the error in measuring the absolute fluorescence intensity.

The method is applicable for determining the concentration of diatomic molecules in highly spaced pairs available

for research using the laser-induced excitation beam and to its luminous excited fluorescence under conditions of vector E using a monochromator when the minor role of collision type DFS-12 (inverse to dispersive effects in the area of 0.5 nm / mm, width input and output

slit 1.2 mm). At the same time exciting.

grain beam (for example, Na-, K

2 2

Those,

2

NaK, Se, etc.). The method is experi- mentally parallel to the entrance slit and tested on K and Na molecules. The fluorescence zone passes through the end pairs of the corresponding elements. The dependence of the degree of polarization on the parameter x optical slit. Fluorescence is recorded using a PMT-79 photomultiplier in the counting mode, photons. Degree of polarization

pitching was also measured for Te and NaK molecules. The concentration range of the studied molecules is approximately

I am 13

10-10. It is determined by the sensitivity of the detection of fluorescence (lower limit) and collisions that cause the destruction of optical pumping, and the reduction of x to X 1 (upper limit).

The method is carried out as follows.

The concentration of diatomic potassium molecules is determined. Saturated potassium vapor heated to T 470 K in

potassium fry heated to T 470 K in

a fluorescence glass cell pre-evacuated to a pressure not worse than 10 Torr is irradiated with linearly polarized radiation of helium-neon

ten%. The average value of the relaxation time during the passage through the beam is about 7.4010 s. The diameter of the diaphragm should be chosen in the range from 1 to 5 mm, since for very small diameters the diffraction background is significant, and with increasing diameter the excitation power density decreases.

Laser excited fluorescence

in the cycle (X ri V 1, l 73) - 40 - (in Pi, v 8, l 73) - (, V 9, l 73), where in Pi are symbols of the electronic terms of the ground and excited state,

v and V - oscillatory quantum

numbers;

-r t-

I and I - rotational quantum

the number of ground and excited states

recorded at right angles to

Those,

2

n-Na xl beam parallel to the entrance slit and the entire fluorescence zone passes through

the gap. Fluorescence is recorded using a PMT-79 photomultiplier in the counting mode, photons. Degree of polarization

measured by alternating automatic switching of the analyzer placed in front of the entrance slit to the position where components I are passed

1 |, or

j, the fluorescence intensity, polarized respectively parallel or perpendicular to the vector E of the exciting light, the syn-concentration of K molecules at the vibrational-rotational level from which the laser beam is absorbed, is calculated as n ,, 1 / Box

one-time counters are switched chronically, where 1 is absolute

electronic pulses that accumulate in two channels with a measurement period in one position, equal to 1 1 s. The total counting time was 100 seconds in each channel. The measured value of the degree of polarization P (1 "- (l ,, + 1e.) 0.4174, which corresponds to the optical pumping parameter equal to x1.138. The values obtained for different temperatures T allow extrapolation to the conditions for highly dispersed vapor, when there is no collisional relaxation in the zone of action of the exciting beam. In these conditions, a value of x 0.768 is obtained.

I

The relaxation time T and the value of the parameter determined from the beam diameter

fluorescence intensity, B o - absorption coefficient; h is Planck's constant. For the example being described, n, -j 2,. The transition to a total of 15 molecular concentration. U-2 is carried out for the Boltzmann distribution over the vibrational-rotational levels at a given temperature. As a result, the determined value of the concentration is (9 ±

20

+ 3) W cm h

Claims (1)

Invention Formula 25 The method for determining the absolute concentration of diatomic molecules in high-density pairs, including their laser irradiation, measuring the absolute intensity of air, allows calculating the coefficient of laser-induced fluorescence of two-atomic molecules, calculating the coefficient BP absorption of 1.04–10 s with a relative error no worse than 10%. The absolute fluorescence intensity is measured by comparing with the SI-10-300 reference ribbon lamp, the radiation of which was attenuated by more than 10 times graduated filters. To calculate the concentration of K molecules, at the EKV level (CT, v, and -, l -3 35 absorption, determination of the concentration of diatomic molecules by the ratio of the absolute intensity and the absorption coefficient, characterized in that, in order to increase the accuracy and reliability of the determination, they form a uniform distribution of radiation over the circular transverse 1.1 73), from which the laser beam is absorbed, determine the degree of polarization of the laser-excited fluorescence, and the absorption coefficient are calculated from the degree of polarization and the diameter of the circular cross-section of the laser radiation. laser radiation, the following radiation constants were used: spontaneous decay time, 6 ns, Einstein transition coefficient of fluorescence (Pi, V 8., I 73) - Compiled by V.Dorofeev Editor A.Revin Tehred M.Hodanich Proofreader V.Girn to Order 6396/32 Circulation 776.Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4 - (X Z ;, V 9, I / 73), for an hour equal to A, Tote L1, 4.529 10 3.03-10 s14 ,, - 1 The concentration of K molecules at the vibrational-rotational level from which the laser beam is absorbed is calculated as n ,, 1 / Box x, where 1 is absolute x, where 1 is absolute fluorescence intensity, B o - absorption coefficient; h is Planck's constant. For the example being described, n, -j 2,. The transition to the total concentration of molecules. U-2 is carried out for the Boltzmann distribution over the vibrational-rotational levels at a given temperature. As a result, the determined concentration value is (9 ± + 3) W cm h Invention Formula The method for determining the absolute concentration of diatomic molecules in highly dispersed pairs, including their laser irradiation, measurement of the absolute intensity of air absorption, determination of the concentration of diatomic molecules by the ratio of the absolute intensity and the absorption coefficient, characterized in that, in order to increase the accuracy and reliability of the determination, they form a uniform distribution of radiation over the circular transverse the degree of polarization of the laser-excited fluorescence, and the absorption coefficient are calculated from the degree of polarization and the diameter of the circular cross-section of the laser radiation.