1. Gothenburg Riga Ion Beam Apparatus GRIBA- Status and Perspectives U. Berzinsh, J. Blahins, A. Apsitis, A. Rieba1 J. Klavins, O. Windelius, J.-Å. Wiman and D.Hanstorp Riga, 2014.02.07

2. Bacground The construction of GRIBA (Gothenburg Riga Ion Beam Apparatus) is a collaboration between University of Latvia and University of Gothenburg. It was started in frame work of FP7 FOTONIKA-LV in the beginning of year 2012. Equipment available at University of Gothenburg has been used to construct an ion beam apparatus. Many visits from Riga to Gothenburg have been performed during the two years of the project. The main work of the construction has been performed by the Riga group. Recently the first ion beam of Cl anion was transported through the apparatus. Our main idea is to build an apparatus from few easy transportable modules: 1) ion source with mass selector, 2) experimental chamber with electron spectrometer, and 3) Laser system. The apparatus will be used for studies of the photodetachment process of atomic and molecular negative ions.

3. GRIBA

4. Colutron Ion Gun, drawing

5. Colutron Ion Gun, diagram

6. Ion beam sources and experimental chamber (taken from U.Ljungblad dissertation)

7. Negative ions Negative ions are interesting from a fundamental point of view. Experimental studies of negative ions can therefore serve as a probe of electron correlation and hence can be used to test theoretical models that go beyond the independent particle approximation. The scientific interest in negative ions is not only at the fundamental level. Most importantly, they play a decisive role in all types of plasmas. Knowledge about the production, detection and destruction of negative ions are therefore of vital importance in fields such as: –microelectronics, –light sources, –atmospheric sciences, –fusion research. – Accelerator Mass Spectrometry (AMS), currently the most sensitive trace element analysis method. A prerequisite in AMS is that the sample under investigation is injected into the accelerator in the form of negative ions. –Astrophysics is another field where negative ions play a key role. It has been taken for granted that negative ions are very important in the molecular process in interstellar media, but it wasn’t until 2006 that the first negative ion, CH6-, was observed. Since then the field has blossomed, with a large activity both at astronomical observatories and in laboratories.

8. PROPOSED EXPERIMENTS Determination of energy of excited states in atomic negative ions. The electron energy spectra from the negative ions will directly reveal the energy levels in a negative ion. We did earlier a measurement of the fines structure splitting of As-. Similar experiements for other elements are of interest. We need to find states that are not so accurately determined. Secondly, we need to be able to produce them with the plasma source. This is not clear at the moment. A particular interesting case is W. We know that there is an excited state, but its energy is unknown. Energy spectra of molecular negative ions. There are many molecular negative ions with unknown energy levels. The problem here is that the spectra might be so complex that it could be hard to interpret the results. Here a good literature search is need. Carbon chains could here be of particular interst since they are relevant from an astrophysical point of view. Other interesting case could be hydrides of ions of interest in AMS. Angular distribution of electrons from molecular negative ions. This is a complementary study from the one above. By rotating the polarisation we can se the angular distribution of the emitted electrons. This will give information about the symmetry (s or p) of the state. This can help to identify complex spectra. To finish the studies on Al-, Al2-, Al3-that we never published. Could be followed up.