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Laser Experiments Reveal New Insights into Metal Core at Center of Earth

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Using high-energy laser beams and optical sensors, a scientific team from the University of Edinburgh has conducted experiments to replicate conditions at Earth’s core.

Scientists observed the behavior of nitrogen samples at more than one million times normal atmospheric pressure and at temperatures above 3000 °C. To do so, the team combined static and dynamic techniques in single-pulse laser heating experiments on precompressed N2 samples in a diamond anvil cell, with in situ time-domain measurements of optical emission, transmission, and reflectance in the visible spectral range (480-750 nm) using a streak camera. The sample was heated via the energy transport of an NIR (1064-nm) laser focused down to approximately 10 μm.

The optical spectroscopic probes, aligned to the heated spot, were used in a confocal geometry that suppressed spurious probe signals. Transient transmittance and reflectivity were obtained using pulsed broadband supercontinuum (1 MHz, 150 ps, 480-720 nm) and occasional continuous laser (532 nm) probes.

The team’s discovery — that under such extreme conditions, nitrogen exists as a liquid metal — could aid understanding of how the planets were formed. It could also provide insight into how Earth’s atmosphere evolved and how it could develop in the future.

“Earth’s atmosphere is the only one of all the planets where nitrogen is the main ingredient — greater even than oxygen,” said researcher Stewart McWilliams. “Our study shows this nitrogen could have emerged from deep inside the planet.”

The research was published in Nature Communications (doi:10.1038/s41467-018-05011-z).

Photonics Spectra
Sep 2018
Research & TechnologyeducationEuropelasersopticsspectroscopySensors & Detectorsoptical spectroscopycontinuous wave lasersprobespulsed lasersenvironmentTech Pulse

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