In this paper, a model of cavitational luminescence (CL) and sonoluminescence (SL) is developed. The basis of the model is the PeTa (Perel'manTatartchenko) effect-a characteristic radiation under first-order phase transitions. The main role is given to the liquid, which is where the cavitation occurs. The evaporation of the liquid and subsequent vapor condensation inside the bubble are responsible for the CL and SL. Apparently, the dissolved gases and other impurities in the liquid are responsible for peaks that appear at the background of the main spectrum. They most likely are excited by a shock wave occurred during cavitation. The model explains the main experimental data. Thus, no mystery, no plasma, no Hollywood.

This paper is a continuation of one published in this journal nine months ago. The two papers present a model of cavitational luminescence (CL), multi-bubble sonoluminescence (MBSL), one-bubble sonoluminescence (OBSL), and laser-induced bubble luminescence (LIBL). The basis of this model is the PeTa (Perel'manTatartchenko) effect, a nonequilibrium characteristic radiation under first-order phase transitions, especially vapour condensation. In this model, the main role is given to the liquid, where the evaporation, condensation, flash, and subsequent collapse of bubbles occur. The instantaneous vapour condensation inside the bubble is a reason for the CL/MBSL/OBSL/LIBL. Apparently, the dissolved gases and other impurities in the liquid are responsible for peaks that appear at the background of the main spectrum. They are most likely excited by a shock wave occurred during the collapse. This paper, in contrast to the previous one, presents a slightly expanded model that explains additional experimental data concerning especially the LIBL spectrum. As a result, today we are not aware of any experimental data that would contradict the PeTa model, and we continue to assert that there is no mystery to the CL/MBSL/OBSL/LIBL phenomena, as well as no reason to hope that they can be used for high-temperature chemical reactions, and even more so for a thermonuclear ones.

This paper is the third in a series published in this journal during 2017-2018. These three papers present various stages in the development of the PeTa model for phenomena of the same physical nature: cavitational luminescence (CL), multi-bubble sonoluminescence (MBSL), single-bubble sonoluminescence (SBSL), and laser-induced bubble luminescence (LIBL). The basis of this model is the PeTa (Perel'man-Tatartchenko) effect-a nonequilibrium characteristic radiation under first-order phase transitions, for instance, vapour condensation. The third iteration of this model "Vapour bubble luminescence" (VBL) is presented in this paper. The essence of this model is as follows: with a local decrease of pressure or an increase of temperature in a tiny volume of the liquid, one or several bubbles filled with vapour will appear. Subsequently, a very rapid increase in pressure or a decrease in temperature of the bubble leads to super-saturation of the vapour inside the bubble, followed by its instantaneous condensation with the emission of condensation energy (this is the PeTa effect). A sharp decrease in pressure causes the collapse of the bubble accompanied by a shock wave in the liquid. VBL model is conveniently represented on the solid-liquid-vapour phase diagram. A better understanding of the physical nature of the phenomena under consideration could help to find their useful applications. To develop this idea further, we propose a design of a cavity-free pulsed laser on the basis of CL/MBSL/SBSL. An analysis of LIBL in cryogenic liquids is also given in this paper.

Crystallization and vapor condensation are considered as the processes of sequential penetration of single atoms/molecules into condensate. In the course of these transitions the transitive radiation must be generated, which would carry away the liberated latent heat by photons of characteristic frequencies. The transient radiation is examined by the general Ginzburg-Frank theory. The emission of defined frequencies determined by the values of liberated latent heat is confirmed by analyses of several experiments of authors and other researchers.

This paper presents new experimental evidence of the PeTa effect-infrared characteristic radiation under first order phase transitions, especially the crystallization of melts and the deposition and condensation of vapours/gases. The PeTa effect describes the transient radiation that a particle (i.e., atom, molecule or/and cluster) emits transient radiation during a transition from a meta-stable higher energetic level (in a super-cooled melt or a super-saturated vapour) to the stable condensed lower level (in a crystal or a liquid). The radiation removes latent heat with photons of characteristic frequencies that are generated under this transition. The abbreviation "PeTa effect" means Perel'man-Tatartchenko's effect.