Study of Hydrogen and Oxygen and Its Reaction With Host Elements in Sandstone by Laser-Induced Breakdown Spectroscopy (LIBS)

A study of hydrogen and oxygen and its reaction with host elements in a sandstone has been done by laser-induced breakdown spectroscopy (LIBS). The sandstone was irradiated by Nd-YAG laser (1064 nm, 7 ns) with varied energy of 60 mJ till 140 mJ in surrounding air gas pressure of 1 atm and produced plasma. The emission intensities of hydrogen H I 656.2 nm and oxygen O I 777.2 nm in the plasma were captured by HR 2500+ spectrometer and displayed in intensity as a function of wavelength. The data show that the emission intensities of hydrogen and oxygen increase with increasing laser energy at a gradient of 5.4 and 11.8 respectively every increasing laser energy of 20 mJ. To characterize the reaction process between hydrogen and oxygen with the host elements of the sandstone, a 0.2 ml demineralized water was dropped on the sandstone surface and was analyzed as a function of delay time reaction and temperature. The data show that the oxidation reaction between host elements and oxygen occurred after 25 minutes that the oxygen emission intensity increases and the hydrogen emission intensity decreases. Another data also show that the increasing temperature of sandstone until 80 C increased intermolecular bond between oxygen and host element and dehydrogenation took place after reaching this temperature