Sand in the laboratory. Production and interrogation of gas phase silicates. Damian L Kokkin and Timothy Steimle.

Silane + Oxygen and its importance Technological importance. SiO 2 and SiO 3 formed on silicon surface through oxidation process. Formation of silicate dust grains in the ISM. Second row analogue to carbon + oxygen Previously most experimental studies have been undertaken in rare matrices with limited gas phase studies. – Matrix IR SiO 2 : Andrews 1992 – Matrix IR SiO 3 : Trembley et al – PES Si x O y : Lai-Sheng Wang et al – PIE SiO, SiO 2 : Kostko 2009 Theoretically challenging. – SiO 3 : Beste 2002 and Grein Predicted visible transitions. – Si x O y : Nayak 1998, Chu 2001 Kinetic Studies. – Si + O containing: Gómez Martín 2009 & 2011, Hao 2014 Yang et al. Applied Physics Letters, 86, , 2005

Experimental Approach Excitation laser Counts λ em Grating Mirror 0.67m McPherson monochromator with Andor iStar cooled intensified CCD camera. SiH 4 (2%) + N 2 O/O 2 (<0.2%) in argon buffer gas (300psi)

Experimental Approach Excitation laser Counts λ em Grating Mirror 0.67m McPherson monochromator with Andor iStar cooled intensified CCD camera. SiH 4 (2%) + N 2 O/O 2 (<0.2%) in argon buffer gas (300psi)

2D spectrum from SiH 4 +N 2 O Discharge. ASE pumping SiH 2

SiO 3 Theory – Vertical Excitation Energies eV Excitation of our unknown. Energy (cm -1 )  Energy (cm -1 ) eV Spacing 2.6cm -1 → A rotational constant of 5.2cm -1

DF of our unknown. ? Ground State Frequency (cm -1 ) Matrix IR on SiO 3 : 287cm cm cm cm cm Calculated 507cm -1 ?

What else do we know. Lifetime: 1970±72ns No obvious shift or new peaks in spectrum when D 2 is added to the reaction mixture. – Tried discharging SiCl 4 as a precursor to remove hydrogen completely. Problems. – Lead to the first detection of SiHD. At pulsed dye resolution no shift in spectrum is discernable in an external magnetic field. Spectrum enhanced slightly with the addition of a small amount of oxygen. Too much oxygen results in only observing SiO and clogging the nozzle.

Confirmation of the SiO 3 assignment as carrier of observed spectrum? Started trying to produce these spectral features with ablating a silicon rod in the presence of oxygen. Try to keep the oxygen and silane apart until the discharge to reduce the production of sand in the reaction cylinder. Try to measure the REMPI-TOFMS spectrum. – Problems may arise due to silicates having very high IPs.

Acknowledgements National Science Foundation, Division of Chemistry grant, CHE