Shock waves, emission from

Fig. 5.4. Schematic evolution of the internal structure of a star with 25 times the mass of the Sun. The figure shows the various combustion phases (shaded) and their main products. Between two combustion phases, the stellar core contracts and the central temperature rises. Combustion phases grow ever shorter. Before the explosion, the star has assumed a shell-like structure. The centre is occupied by iron and the outer layer by hydrogen, whilst intermediate elements are located between them. CoUapse followed by rebound from the core generates a shock wave that reignites nuclear reactions in the depths and propels the layers it traverses out into space. The collapsed core cools by neutrino emission to become a neutron star or even a black hole. Most of the gravitational energy liberated by implosion of the core (some 10 erg) is released in about 10 seconds in the form of neutrinos. (Courtesy of Marcel Amould, Universite Libre, Brussels.)...

Protons, nuclei and electrons in cosmic rays would appear to inherit their energy spectrum from this mechanism, associated with shock waves. A non-thermal component in X-ray emissions from the recently discovered remnant of the 1006 supernova provides direct confirmation. 

Palmer137 has observed emission from bromine in the hot equilibrium gas behind a shock wave, in the temperature range 1300-2500 °K. The emission spectrum appeared to be a continuum, with several broad maxima in the range 4000-6100 A, though the resolution was presumably not adequate to distinguish a continuum from a dense band spectrum. Comparison was made of observed activation energies for emission at various wavelengths with predictions based on the simplest possible application of the Franck-Condon principle to the potential curves. The results... 

Type II supernovae are massive stars, ones that progress in their nuclear fuels well past the fusion of carbon and the fusion of oxygen at their centers. When their cores run out of nuclear fuel, those central regions collapse to form a neutron star, or in some cases a black hole. The incredibly intense emission of neutrinos from the newly born neutron star so heats the overlying layers, aided by an outward moving shock wave of pressure, that those layers pardy explode and are ejected. The last of these thatwas visible to the naked eye occurred in 1987, and demonstrated for the first time the correctness of the intense neutrino burst that is their main energy output. 

Herbig-Haro objects emission-line nebulae which are produced by shock waves in the supersonic outflow of material from young stars also referred to as Herbig-Haro nebulae. 

Sato, Tsuchiya, and Kuratani [216] have solved the relaxation equation for the vibrational energies of two diatomic gases A and B diluted in an inert monatomic gas M, and have applied the solution to shock-wave relaxation profiles in order to obtain V-V transfer rates. Their solution shows that the relaxation of each of the component molecules proceeds as if it possessed two relaxation times. At the onset of the relaxation process, both components begin to relax with their respective V-T rates, whereupon the relaxation rate of that component having the smaller V-T relaxation time begins to decrease, while the relaxation rate of the other component increases. Finally, both components relax with the same rate toward their equilibrium states. By observed infrared emission from the CO fundamental behind shock waves in mixtures of CO-N2, C0-02, CO-D2, and CO-H2, they were able to determine Pil as a function of temperature. Argon was used as inert buffer gas. 

Supernova explosions produce spherical shock waves with stellar remnants. The shock wave propagates into interstellar space and dynamically interacts with the ambient interstellar clouds. Yusef-Zadeh et al. [48] reported that shock-excited OH maser emission outlined the galactic center supernova remnant. Aschenbach et al. [49] suggested that the X-ray emission associated with the ejected objects was produced by shock heating of the ambient medium resulting from supersonic motion of the objects. 

The decomposition in argon diluent behind incident shock waves has been observed by measuring the infrared emission from HF for various mixtures over a temperature range 3700—6100°K [114, 115]. The proportionality of emission signal to HF concentration was demonstrated to hold over the temperature interval investigated and for optical densities of 0.01—0.5 atm cm. 

Fig. 2.8. Experimental values of the logarithm of /2[02l against reciprocal reflected shock wave temperature for exponential growth data from various sources. 17 = 10 CO-0 flame spectrum emission measurements from Reference 62, a infrared emission measurements from Reference 74. rj = 0 33 C0 0 emission measurements from Reference 63 for various ranges of total reflected shock gas concentration and identical mole fractions of H2 and O2. 015 — 1 4 x lO moles liter . t 1 6 — 3-7 x 10 moles liter. 5-5 — 9 2 x 10 moles liter. Solid line = 9 5 x lO exp (—15 000/Rr) cm ...

In most of the methods, CO2 is decomposed into CO and O2. The decomposition of CO2 by Davis et al. (Mahesh Akira, 2010) was performed using a C02-argon gas mixture in a shock tube where the temperature varies from 2600 to 1100 K. The rate of decomposition of CO2 using shock waves is monitored by observing the infrared radiation. However, there is an initial rapid rise in the infrared emission when the shock wave passes through the system. It should be noted that the infrared emission decays exponentially and shows the decomposition of CO2 into CO and O2. 

There is published evidence of acoustic emission from cathode streamers. The acoustic shock waves produced as the 3rd cathode mode propagates have been photographed (Kelley and Hebner, 1981a). In addition, a barium titanate ultrasound transducer has been used to measure the acoustic signals directly (Nelson and McGrath, 1975). This study... 

In the thermal decomposition of N2H4 in shock waves, NH(X) is formed in secondary reactions [20]. In shock-heated NH3-noble gas mixtures at high temperatures (T>3000 K) [37 to 39] and in a high-temperature plasma (T = 3200 K), emission from NH(A) was observed [40]. At lower temperatures in shock waves NH(X) was observed [41]. HN3 and HNCO can be pyrolyzed at significantly lower temperatures (T> 1200 K) under these conditions mainly NH(X) is formed [44, 45]. 

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