Behavior of Long-Chain Hydrocarbons at High Pressures and Temperatures

Area of Science:

• Geochemistry
• Astrochemistry
• Materials Science

Background:

• Long-chain aliphatic hydrocarbons are found in meteorites, but their origin (pristine extraterrestrial or terrestrial alteration) is debated.
• Understanding their stability under extreme conditions is crucial for determining their indigenous nature.

Purpose of the Study:

• To investigate the behavior of aliphatic hydrocarbons under simultaneous high pressure and temperature.
• To explore the effects of thermal changes on molecular structure, bridging a gap in current research.

Main Methods:

• Utilized a resistively heated diamond anvil cell to subject aliphatic hydrocarbons to simultaneous high pressure and temperature.
• Employed Raman spectroscopy to monitor structural changes via vibrational modes.

Main Results:

• Observed new low-energy vibrational modes upon compression, consistent with chain bending.
• Documented softening of these modes upon heating to ~220 °C, indicating molecular unbending and anharmonicity.

Conclusions:

• High pressure and temperature significantly alter the molecular structure of long-chain aliphatic hydrocarbons.
• These findings provide insights into the potential for indigenous extraterrestrial organic molecules in meteorites.