Soft x-ray photoabsorption spectra of photoionized CH₄and CO₂plasmas

Abstract

In this work we report soft x-ray (SXR) photoabsorption measurements in neutral methane and carbon dioxide molecules and their corresponding photoionized plasmas. The SXR radiation was generated by a table-top laser produced plasma source based on a double stream gas puff target. At low SXR intensities only features related to neutral molecules are present in the absorption spectrum. On the other hand, as the radiation intensity increases, we observe new absorption features in the low photon energy side of the spectrum. In that case fragments such as neutral and ionized molecules, atoms and atomic ions are found to contribute to the absorption spectrum of the plasmas. To our knowledge these are the first measurements where this laser plasma based SXR source is used to both create and probe a molecular plasma. Emphasis is placed on identifying the fragment species and the corresponding transitions.

Oxygen K-shell photoabsorption spectra of photoionized CO2plasmas

“…The calibration of the spectrometer was performed by means of the emission spectrum of a gas mixture (N 2 : O 2 : Ar (1 : 1 : 1)) prior to the SXR photoabsorption measurements. A detailed description of the setup can be found in reference [39]. The radiation emitted by the LPP plasma source then served a twofold role: first, it created the photoionized molecular plasma and secondly, it emitted the radiation that acted as the backlight for probing the molecular plasma.…”

“…Carbon K-shell photoabsorption measurements for photoionized CH 4 and CO 2 plasmas have been recently reported using an LPP source based on a double-stream gas puff target [39]. In this work we use the same SXR source to perform oxygen K-shell absorption measurements on neutral and photoionized CO 2 plasmas.…”

The 5d-6p VUV Photoabsorption Spectrum of Bi+

“…Analogous measurements yielding relative photoabsorption cross sections can be performed by means of table-top or laboratory scale techniques. One possibility is to perform photoabsorption measurements in atoms and the corresponding photoionized plasmas using radiation emitted from a laser produced plasma (LPP)-based source where a gas target serves as the active medium [14][15][16]. Another well-established method is the so-called dual laser plasma (DLP) technique [17,18].…”