Proton impact excitation of SO₂

Abstract

These results indicate that perhaps protons play a larger role in the torus than was previously thought. Since a review of the literature and databases shows no measured photon emission cross sections for protons colliding with SO2, we have initiated a determination of these cross sections. We present here spectra and preliminary cross section data for proton-SO2 collisions over a range of proton energies from 50 to 250 keV. This range of energies dominates the proton energy flux. Experimental Details General DescriptionMore information on the general nature of the experimental techniques employed by this laboratory can be found in previous publications [Monce, 1988[Monce, , 1990Freeman et al., 1992]. However, as this is the first publication utilizing a CCDspectrometer system for detection of the photons, we will describe the procedure in greater detail.The The target gas cell is aligned along the beam path with an adjustable viewing slit along this length. The target gas enters the cell through a tube in the top. A tube at the bottom is connected to a capacitance manometer for pressure measurement. The gas pressure is regulated with a precision needle valve. Also in the target gas cell is a thermistor for temperature measurement. The thermistor was calibrated using a 0.1øC mercury thermometer.The photons emitted 90 ø to the beam path are collected and 26,147

Middle ultraviolet and visible spectrum of SO2 by electron impact

“…At 18‐eV electron impact energy the features identified on top of the underlying continuum below 400 nm wavelength are mostly SO(A,B) vibrational bands. At 98‐eV electron impact energy the additional processes of dissociative (ionization) excitation produce a myriad of hundreds of O I, O II, S I, and S II features mostly above 380 nm and up to 600 nm [ Kiehling et al , 2001]. Clearly, the spectra at all electron impact energies extend beyond the previously reported value of 460 nm [ Miller and Becker , 1987].…”

“… b From NIST web site (http://physics.nist.gov) list of atomic physics transitions and from [ Kiehling et al , 2001]. …”

“…Each of the O I lines at 394.7, 395.4, 436.8, 503.7, and 533.0 nm mentioned by Miller and Becker [1987] is clearly visible. A recent laboratory paper by Kiehling et al [2001], which measured proton impact emission cross sections of SO 2 , has observed scores of strong O I, O II, S I, and S II lines without blending from the SO 2 quasicontinuum of electronic transitions found in low‐energy electron impact emission experiments. The same strongest features are identified in Figure 3 by the peak position.…”

Middle UV to near‐IR spectrum of electron‐excited SO2

“…The O I, II and S I, II emission features from dissociative excitation were found to be weak in comparison to the integrated cross section of the molecular emissions of MUV1 and MUV2. A few years later Kiehling et al [2001] investigated the VOIR spectrum from 3800 to 8000 Å produced by proton impact on SO 2 . Kiehling et al found the molecular features to be weak in comparison to the scores of O I, II and S I, II atomic Rydberg series.…”

Absolute photon cross sections for Balmer lines from proton‐SO2 collisions

“…Collisions between these protons and the various species of atoms and molecules present in the Io ejecta are a likely source of emission and may be competitive with electron collisions in particular regions of the Io environs. In a previous article [ Kiehling et al , 2001] we presented the emission spectrum produced by H + –SO 2 collisions in the wavelength region of 380–800 nm which showed numerous lines from neutral and ionized sulfur and oxygen. That work also showed strong Balmer lines from hydrogen.…”