Luminescence from laser-created bubbles in cryogenic liquids

Area of Science:

• Laser-induced cavitation physics
• Plasma spectroscopy
• High-temperature material analysis

Background:

• Laser-created bubbles in liquids generate shock waves and light emission.
• Previous studies focused on bubble dynamics and general light emission spectra.

Purpose of the Study:

• To investigate the luminescence from laser-created bubbles in pressurized liquid nitrogen and argon.
• To analyze the spectral content and temporal characteristics of the emitted light.
• To determine the temperature and origin of the observed atomic emissions.

Main Methods:

• Generation of bubbles in pressurized liquid nitrogen and argon using laser pulses.
• Observation and analysis of luminescence pulses during bubble collapse.
• Spectroscopic analysis of the emitted light to identify atomic species and measure intensities.
• Correlation of light pulse duration with bubble size and analysis of spectral line intensities.

Main Results:

• A luminescence pulse was observed at the first bubble collapse point.
• Light pulse duration scaled linearly with bubble size (0.2–1 mm), ranging from 200 ns to 1 µs.
• The spectrum contained unexpected strong atomic lines of neutral chromium, attributed to stainless steel microflakes.
• Bubble collapse heated the chromium to approximately 4500 K, as determined from spectral line intensities.

Conclusions:

• Laser-induced bubble collapse in liquid gases can generate high temperatures and emit light spectra influenced by contaminants.
• Stainless steel microflakes, ablated by shock waves, are vaporized and ionized within the bubbles, leading to chromium emission.
• The study demonstrates a method for estimating high temperatures within collapsing laser-induced bubbles using atomic line spectroscopy.