Vibrational Infrared Lifetime of the Anesthetic nitrous oxide gas in solution

TL;DR

This study measures the vibrational lifetime of nitrous oxide in octanol and olive oil using ultrafast infrared spectroscopy, revealing that energy relaxation is mainly influenced by the hydrophobic environment, aiding understanding of anesthetic mechanisms.

Contribution

It provides the first experimental vibrational lifetime measurements of N₂O in biologically relevant solvents, linking solvent hydrophobicity to anesthetic energy relaxation mechanisms.

Findings

Vibrational lifetime of N₂O is ~55 ps in olive oil.

Vibrational lifetime of N₂O is ~52 ps in octanol.

Energy relaxation is primarily governed by the hydrophobic nature of the environment.

Abstract

The lifetime of the asymmetric fundamental stretching 2218 cm$^{-1}$ vibration of the anesthetic gas nitrous oxide (N$_2$O) dissolved in octanol and olive oil is reported. These solvents are model systems commonly used to assess anesthetic potency. Picosecond time-scale molecular dynamics simulations have suggested that protein dynamics or membrane dynamics play a role in the molecular mechanism of anesthetic action. Ultrafast infrared spectroscopy with 100 fs time resolution is an ideal tool to probe dynamics of anesthetic molecules on such timescales. Pump-probe studies at the peak of the vibrational band yield a lifetime of $55 \pm 1$ ps in olive oil and $52 \pm 1 ps$ in octanol. The similarity of lifetimes suggests that energy relaxation of the anesthetic is determined primarily by the hydrophobic nature of the environment, consistent with models of anesthetic action. The results show that nitrous oxide is a good model system for probing anesthetic-solvent interactions using nonlinear infrared spectroscopy.