Absorption cross section of gas phase isoprene in the infrared-visible range

Casper Vindahl Jensen, Vera Staun Hansen, Sofie Markussen, Anisha Iyer, Henrik G. Kjaergaard*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We have recorded the gas phase spectrum of isoprene at room temperature from the mid-infrared range and into the visible range (600 cm−1 to 17050 cm−1). Absorption spectra were obtained by Fourier transform infrared, conventional dispersion ultraviolet–visible-near-infrared and cavity ring-down spectroscopy to cover the entire range with a resolution comparable to that of the instruments on the James Webb Space Telescope. We have assigned the CH-stretching fundamental and overtone bands corresponding to the ΔvCH=1−6 transitions based on anharmonic vibrational calculations using normal mode and local mode models, for the lower- and higher-energy regions, respectively. We have determined accurate absolute intensities of the observed CH-stretching regions and compare with existing experimental values and with theoretical results. The accuracy of our absolute band intensity is about 2% in the fundamental region and about 10% in the 6 orders of magnitude weaker highest overtone region. Our spectrum can facilitate the detection and possibly quantification of isoprene in planetary atmospheres.

Original languageEnglish
Article number125667
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Volume330
Number of pages10
ISSN1386-1425
DOIs
Publication statusPublished - 2025

Bibliographical note

Publisher Copyright:
© 2025 The Authors

Keywords

  • Bio-signature
  • Cavity ringdown spectroscopy
  • Fundamental and overtone transitions
  • JWST
  • Local mode models
  • Vibrational band intensities

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