22
1 Resonance Methods for Increasing Sensitivity of Interferometry …
from the condition γ = 1/2 and produced by integral method is 0.57 mm, and only
by holographic method—0.60 mm.
The observed divergences to a large extent can be connected with the simplest
approximation of distribution of I 0 (r) and I i (r) by the Gaussian law. In this simplest
approximation, the connection between half-width I i , I 0 and γ is specified by the
relation:
x
2
j =
x
2
0 (2x
2
i − x
2
0 )
x
2
0 − x
2
i
.
(1.25)
At laser pumping by nanosecond pulses, the sizes of coherence areas in the direction of pulse distribution considerably depend on the pumping energy. But the value of
relation of coherence area to generating region square does not practically change.
Concentration changes do not affect diffraction efficiency (in the interval corresponding to absorption constant of 10–18 cm
−1 for λ = 347.2 nm). During scanning
hologram laser end by narrow beam of He–Ne laser, the form of the reconstructed
image has not practically changed. That indicates the absence of the modes over
TEM 00 .
1.3 Resonance Method for Increasing Interferometry
Sensitivity in the Studies of Low-Temperature Sodium
Plasma
Resonance methods for increasing interferometry sensitivity are based on the interferograms recording in the radiation light, which is close in frequency connected
with the absorption line of one of the components of the substance under study (e.g.,
sodium, lithium, potassium plasma and so on). For the first time, obtaining resonance interferograms was proposed by Yu. I. Ostrovsky in 1961 [37]. The idea of
this method is that for plasma probing, we use the radiation with the wavelength is
closely connected with the absorption line of one of the plasma components.
Near the absorption line, which has a dispersive contour [76], atoms and ions
refraction are described in the following way:
n − 1 = Cλ
3
0 N f
λ − λ 0
(λ − λ 0 ) 2 + ((λ/2) 2 ,
(1.26)
where λ 0 is the wavelength corresponding to the maximum absorption line, and
λ is the absorption line width measured at a half-height; λ is the wavelength of
translucent radiation; f is the oscillator line strength; N is the atom concentration on
the absorption level and C = e
2 /4π m e c
2
= 2.24 × 10
−14 cm.
As it comes from (1.26), the refraction of corresponding atoms as it approaches to
absorption lines increases sharply and can enormously exceed the refraction of the
same atoms away from the absorption line. Thus, the usage of wavelength, which
1 Resonance Methods for Increasing Sensitivity of Interferometry …
from the condition γ = 1/2 and produced by integral method is 0.57 mm, and only
by holographic method—0.60 mm.
The observed divergences to a large extent can be connected with the simplest
approximation of distribution of I 0 (r) and I i (r) by the Gaussian law. In this simplest
approximation, the connection between half-width I i , I 0 and γ is specified by the
relation:
x
2
j =
x
2
0 (2x
2
i − x
2
0 )
x
2
0 − x
2
i
.
(1.25)
At laser pumping by nanosecond pulses, the sizes of coherence areas in the direction of pulse distribution considerably depend on the pumping energy. But the value of
relation of coherence area to generating region square does not practically change.
Concentration changes do not affect diffraction efficiency (in the interval corresponding to absorption constant of 10–18 cm
−1 for λ = 347.2 nm). During scanning
hologram laser end by narrow beam of He–Ne laser, the form of the reconstructed
image has not practically changed. That indicates the absence of the modes over
TEM 00 .
1.3 Resonance Method for Increasing Interferometry
Sensitivity in the Studies of Low-Temperature Sodium
Plasma
Resonance methods for increasing interferometry sensitivity are based on the interferograms recording in the radiation light, which is close in frequency connected
with the absorption line of one of the components of the substance under study (e.g.,
sodium, lithium, potassium plasma and so on). For the first time, obtaining resonance interferograms was proposed by Yu. I. Ostrovsky in 1961 [37]. The idea of
this method is that for plasma probing, we use the radiation with the wavelength is
closely connected with the absorption line of one of the plasma components.
Near the absorption line, which has a dispersive contour [76], atoms and ions
refraction are described in the following way:
n − 1 = Cλ
3
0 N f
λ − λ 0
(λ − λ 0 ) 2 + ((λ/2) 2 ,
(1.26)
where λ 0 is the wavelength corresponding to the maximum absorption line, and
λ is the absorption line width measured at a half-height; λ is the wavelength of
translucent radiation; f is the oscillator line strength; N is the atom concentration on
the absorption level and C = e
2 /4π m e c
2
= 2.24 × 10
−14 cm.
As it comes from (1.26), the refraction of corresponding atoms as it approaches to
absorption lines increases sharply and can enormously exceed the refraction of the
same atoms away from the absorption line. Thus, the usage of wavelength, which