1.Charge Exchange between Slow Highly Charged Ions and Neutrals

Charge exchange (CX) between highly charged ions and neutral atoms or molecules is a process where one or several electrons of atom or molecules are transferred on to the projectile ions. It has long been conjectured as a possible source of astrophysical X-ray emission [1]. Recently, solar wind ions charge exchange with neutrals has been confirmed to be responsible for comet’s coma X-ray emission and the diffuse soft X-ray background [2-3]. Important evidence for charge exchange has also been found in the spectra of supernova remnants [4], around star-forming galaxies [5], and in clusters of galaxies [6].

From the fundamental point of view, these CX collisions of astrophysical interest often occur at low collision energies with large total cross sections (10^-15 cm²). The following X-ray emission has high radiative decay rate and rich discrete spectral features etc.,these unique features enable CX to be an important diagnostic entity for astrophysical soft X-ray background in hot astrophysical plasma (10⁶ to 10⁸ K) environment. Essentially, the CX induced soft X-ray emission is determined by nl-resolved state selective capture cross sections and favored by cascade decay of the excited electron (n and l are principal quantum number and angular momentum quantum number, respectively).

The cold target recoil ion momentum spectroscopy (COLTRIMS) apparatus succeeds in measuring the reliable nl-resolved state selective capture cross sections for many years. With this well-developed technique, we proposed a new project where the astrophysical related soft X-ray emission can be obtained by using experimentally derived nl-resolved cross sections and applying well established radiative cascade model. In particular, high-resolution charge exchange state selectivity measurements may offer an entire new window towards understanding soft X-ray background emission, where interaction between cold and hot gas flow is inaccessible to other observations. 

[1] J. Silk and G. Steigman, Phys. Rev. Lett. 23, 597 (1969).

[2] C. M. Lisse et al., Sci 274, 5285 (1996).

[3] P. Beiersdorfer et al., Sci, 300, 1558 (2003).

[4] S. Katsuda et al., ApJ 730, 24, (2011).

[5] J. Liu et al., MNRAS, 420, 3389 (2012).

[6] A. C. Fabian et al., MNRAS, 417, 172 (2011).

2.Gas phase Chemistry induced by Heavy Ion

Molecules in regions of space warmer than the cosmic background, but still extremely cold around 10 K like cold cores of dense interstellar are of great interest for astrochemistry [1]. In these regions, The gas phase molecular complexes include strongly bound aggregates, intermediate-strength hydrogen bound, and weakly bonded van der Waals dimer or polymer. Most of the known interstellar molecule complexes have been identified from their spectra, either rotational spectra or infrared spectroscopy by spectrometer loaded on satellites. These traditional studies have been focused on the molecule composition, density, temperature, and evolution information. Recently, the development of laboratory technique advances these studies to the point where detailed fragmentation of these molecule complexes become available [2], this largely expands our understanding of molecule complexes and basic radicals associated with life building blocks.

[1] M. Larsson et al., Rep. Prog. Phys. 75, 066901 (2012).

[2] J. Ullrich et al., Rep. Prog. Phys. 66, 1463 (2003)