K Line Shape

Brown dwarfs are mysterious sub-stellar objects that possibly link between planets like Earth and Stars, such as the Sun. They are called “failed stars” because their masses are just below the critical values that can sustain fusion, leaving trace amounts of “un-burned” alkali metals in their H2/He-dominated atmospheres. The alkali resonance doublets, for example, potassium around 0.77 µm, lead to “fingerprint” absorption features in the spectral flux measured by space telescopes, and such distinctive observations can provide insight into the physical properties of their stellar atmospheres. Laboratory characterizations of the potassium absorption line shapes are crucial to explain these spectral

observations; yet they are difficult because of the dangers and difficulties in its sample handling and disposal.

I worked on a safe and effective seeding approach that uses potassium chloride as a precursor to produce potassium via shock wave-assisted processes of sublimation, dissociation, and deionization. To resolve the absorption line shapes of the ppb levels potassium in a highly-transient shock condition, tunable diode laser absorption spectroscopy (TDLAS) with >10kHz modulation frequencies was deployed.