Laboratory X-ray absorption of inter stellar molecular and atomic species

TYPEStudent Seminar
Speaker:Itay Gissis
Affiliation:Technion Physics department
Time:10:00 - 11:30
Location:Lidow Asher Peres (502)

The inter-stellar and inter-galactic gas is frequently observed via absorption of X-ray sources1. Astrophysical models used to study this gas have rarely been bench-marked in the laboratory, primarily due to the high-flux X-ray sources required, which are often too expensive to facilitate in academic scale laboratories.

We present a dedicated experiment to measure absorption spectra of such neutral and photo-ionized gas. We developed the GLIDER – a moderate scale  current generator coupled to a gas-puff z-pinch load, to create a controlled X-ray source2. The source is used to photo-excite and photo-ionize gas of the most abundant cosmic elements such as C, N & O, which is injected into the vacuum using a second puff. We measure the absorbed and un-absorbed X-ray spectrum of the source using high resolution spectrometer. We identified near edge absorption fine structure (NEXAFS)3 features.

The experimental setup allows much flexibility in the X-ray source spectrum and abosrber properties. The experiment is highly reproducible and can be carried out dozens of times per day, to produce data of high statistical significance.

We will present the experimental setup, the spectroscopic system and high resolution spectral results of the absorbing gas.


1.  I. Gissis, U. Peretz and E. Behar, “The ionic composition of the local absorber towards 3C 273”, MNRAS,, Jan 21, 2020.

2. I. Gissis, E. Behar, A. Fisher, S. Aricha, E. Yeger, U. Avni, It. Schnitzer, “GLIDER - A pulsed-current generator for laboratory astrophysics X-ray absorption experiments”, Rev. Sci. Inst., Vol. 91, Iss. 2,  Feb 28, 2020.

3. I Gissis, A. Fisher, E. Behar, NEXAFS spectra of molecular gas, in preparation.