57 / 2023-04-11 18:58:32

Pulsed laser heating with time-resolved analysis: A new tool to explore material properties at extreme conditions

nuclear resonance,pulsed laser heating,diamond anvil cell

Pressure, temperature, length and time are inexorably linked, but in more ways than you might think. Hyperfine interactions provide information about microscopic and macroscopic properties of a material, but an even greater wealth of knowledge can be gained through changing pressure or temperature (or both). Indeed our understanding of the planet on which we live is founded on such studies.



Pressure is inversely related to length squared, where samples must be ever smaller to reach higher pressures. Temperature is inversely related to time, but unlike pressure it is not through a fundamental relation but rather a practical one. Samples subjected to high pressures using a diamond anvil cell can be heated to high temperatures using a laser, and conventionally laser heating takes place in continuous mode (constant power) over long periods of time (minutes to hours). This approach is subject to unwanted effects, however, and ultimately limits the maximum achievable temperatures due to diamond failure.



To overcome these limitations, a group I was part of developed a pulsed laser heating system where samples are heated in a short pulse (on the order of microseconds) followed by a “dark” period. This cyclic procedure makes time also a variable, in addition to pressure and temperature. The laser pulse can be synchronized with nuclear resonance spectroscopic techniques to collect data gated over two different time regions (“hot” and “cold”) over the long periods (minutes to hours) required to obtain a reasonable signal to noise ratio. In further developments, we added time discrimination through time to digital converters where each nuclear resonance data point contains a time stamp to achieve fully time resolved data collection. The presentation will showcase results already achieved and provide a tantalizing glimpse of discoveries yet to come.