SELF

46

S.B. Karavashkin and O.N. Karavashkina

At such conditions a small external excitation is enough, the destabilised system to radiate at the band 21 cm. Rather to say, it would begin luminescenting at this wavelength, as in this case the excitation of oscillations will occur by the energetic scheme of spontaneous luminescence specific for the conditions of interstellar gas shown in Fig. 11.

According to this scheme, the exciting light with the frequency   corresponding to the optic range activates the single electron of hydrogen atom to some unstable excited state. Due to this, the electron radiates an EM wave of some smaller frequency ₁  and returns to the metastable level, violating in this way the energetic balance between the metastable and main levels of the hydrogen atoms in the interstellar gas. With it, the atom can radiate the radio quantum with the essential time delay, as in this case the statistical laws of interaction of the assemblages of particles in gas come into effect. In consequence of it, one of the neighbouring atoms will radiate this radio quantum, while the considered atom will temporary pass to the excited state. As a result of such multiple process, the gas will absorb one quantum of frequency and radiate two quanta ₁ and ₂₁ , violating the known rule of the quantum output conservation. It is important that the first quantum is 'translated' with the decreasing frequency, practically without scattering and with a weak polarisation, and the second quantum will be radiated as the luminescence, so this quantum gains the considerable degree of polarisation and scatters in full accordance with the properties of fluorescent radiation, but at the range of radio waves. With it the condition of the energetic balance will fully remain, since

and the interstellar gas retains its average kinetic temperature.

Given

the light frequency change in a single interaction will be also negligibly small. But on distinct of usual luminescence, the 'translated' quantum will be able to excite the oscillations of the next atoms, gradually with the distance decreasing its frequency and producing the radiation 21 cm. Rather, the interstellar gas itself will gradually transform the EM energy of the optic range into the frequency of balanced heat oscillations of gas, averaging the concentrated fluxes of energy going through it.

So at the conditions of low temperature and rarefied gas, a special type of spontaneous luminescence arises. It originates the displacement of spectral lines of optic range to the red side of spectrum and the scattered radiation in radio range.

To corroborate the scattered pattern of radio fluorescence, we present in Fig. 12 two diagrams of isophotes of the radio waves radiation of the interstellar gas of our Galaxy taken from [26, p. 282, Fig. 4 and 5] at  = 3,5 m    and  = 22 sm  .

Fig. 12 a. The isophotes of the radio waves radiation at   = 3,5 m ; one unit means 1000 K.

Fig. 12 a. The isophotes of the radio waves radiation at = 22 sm ; one unit means 3,25 K.

Though these diagrams relate to different bands of radiation and  = 3,5 m  is much more than the wavelength which the metastable level of hydrogen atom radiates, these diagrams have much in common. First, they both show the typical annular concentration of the isophotes around the sources of optic radiation with the decreasing intensity from the source to periphery. With it, the sources in diagrams can be superposed. This evidences the secondary pattern of radiation excited by the hot stars that are known to be concentrated in the Galactic plane. Second, we can follow in both diagrams the isophotes concentration to the Galactic plane; this is also caused by the concentration of hot stars near this plane. We can see in diagrams only most hot stars; the rest, being more distanced and less hot, do not form the peculiar concentrations of isophotes, but form the general background of high-intensive radio wave radiation, which evidences the much-scattered radiation. Third, as we said above, the isophotes concentration around the stars location has, on the whole, the annular structure. This evidences the absence of sufficient anisotropy in direction of radiation of the mentioned wavelengths. All the said gives us the grounds to suppose that, despite the essential difference of the wavelength  = 3,5 m  from = 22 sm , the nature of radio waves radiation is common in both cases.