Collision satellites

A collision with a Mars-sized object may have resulted in the formation of the Earth s moon. Our moon is by no means the largest satellite in the solar system, but it is unusual in that it and the moon of Pluto are the largest moons relative the mass of the planets they orbit. Geochemical studies of returned lunar samples have shown that close similarities exist between the bulk composition of the moon and the Earth s mantle. In particular, the abimdances of sidero-... 

Fig. 8. Collision-induced satellite spectrum of Naj around X = 5290 A, due to fluorescence originating from rotational levels populated by collision from the V = 6, / = 43 level in the state, which was excited by the X = 4880 A argon laser line. (From ref.

The Intensity ratio between these satellite lines" and the main fluorescence line yields the absolute cross sections for the different collision-induced rotational transitions, provided the He pressure and the lifetime of the excited Na state are known. Both parameters have been measured, giving cross sections between = 1.5 A for A/ = 1 transitions and 6 = 0.3 A for A/ = 5... 

Thermal emission spectroscopy can be used in middle- and far-infrared spectral regions to make stratospheric measurements, and it has been applied to a number of important molecules with balloon-borne and satellite-based detection systems. In this approach, the molecules of interest are promoted to excited states through collisions with other molecules. The return to the ground state is accompanied by the release of a photon with energy equal to the difference between the quantum states of the molecule. Therefore, the emission spectrum is characteristic of a given molecule. Calculation of the concentration can be complicated because the emission may have originated from a number of stratospheric altitudes, and this situation may necessitate the use of computer-based inversion techniques (24-27) to retrieve a concentration profile. 

Figure 12.4 shows the laser intensity dependence of X-ray emission spectra measured at a pulse duration of 30 fs with C = 5 x 10-6. As the laser intensity increased, the X-ray yields increased in proportion. The Rydberg He-like lines from the lsnp-ls2 (n = 3-6) transitions and the dielectronic satellites from the 1 Is2 transition were especially enhanced, which shows that highly excited states of He-like Ar ions were produced due to intensive ion-election collisions. 

The low Fe abundance in the lunar mantle suggests the Moon-forming impact happened late in Earth s accretion (Canup Asphaug 2001). It may have been the last collision with another embryo. Simulations of terrestrial-planet formation find that low-velocity, oblique impacts are common (Agnor et al. 1999), so that planets like Earth and Venus are likely to experience at least one such impact during their formation. This suggests large satellites may be a common outcome of terrestrial-planet formation. 

The ratio between the w-line, which is predominantly excited by electron collisions (8.1), and the k-satellite, which is populated by dielectronic recombination (8.2), depends on the electron temperature only. The ratio between the w line and the intensity of the collisional excited Li-like satellites (8.5), depends on the density ratio between the Li-like and He-like ions, as the collisional excitation rates for the allowed transitions in the He-like system and in the doubly excited Li-like system are similar. 

Information concerning the interaction potentials of Cs (7S, 5D)-rare gas pairs is obtained by interpreting the temperature dependence of the 6S-7S,5D far wing and satellite profiles. A sensitive laser fluorescence technique is used to obtain the absorption coefficient of the mixture. The collision induced oscillator strength, a rapidly varying function of the interatomic distance in the case of such forbidden transitions, is also deduced. Experimental potentials and oscillator strengths are compared with available calculated values. 

In LEO (ca. 300 km altitude), the ambient gas density and temperature are typically 10 cm and 1200 K, respectively although solar activity and diurnal phase can strongly perturb these values. With an orbital velocity of 7.5-8 km/s, the flux of neutral particles on ram surfaces is 10 m s . This corresponds to approximately ten collisions per atomic surface site per second. Atmospheric collisions lead to satellite drag and torques which hinder attitude control. Degradation of materials on ram-facing surfaces can compromise a spacecraft s flight duration as well. ... 

The resulting products were extracted directly into a mass spectrometer to study their fragmentation in an argon collision chamber, and the atomic composition of the peaks obtained in this marmer was checked by their satellites because of the simultaneous existence of three isotopes of silicon Si (92%), Si (5%), and "Si (3%). An unexpectedly large variety of molecular peaks have been observed, the... 

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