Pure rotational Raman spectroscopy applied to N2/O2 analysis of air bubbles in polar firn

Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement,...

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Bibliographic Details
Published in:Journal of glaciology 2021-10, Vol.67 (265), p.903-908
Main Authors: Ohno, Hiroshi, Iizuka, Yoshinori, Fujita, Shuji
Format: Article
Language:English
Subjects:
Air bubbles
Analytical methods
Antarctic glaciology
Bubbles
Channel pores
Firn
Fractionation
Gas separation
Gases
Gravity
ice core
Ice sheets
Oxygen
polar firn
Raman spectroscopy
Rotational spectra
Spectroscopy
Spectrum analysis
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Summary:Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement, little is known about the distribution of air constituents in already closed pores (bubbles) in firn. Herein, we describe the application of high-sensitivity pure rotational Raman spectroscopy, combined with sample immersion in the fluorocarbon-based inert fluid for removing the optical disturbance by diffused reflection. That application efficiently elicits information about nitrogen and oxygen composition ratios (N2/O2 or O2/N2) for each air bubble in firn. The developed methodology presents important implications for elucidating how gas records are formed and modified in the course of pore close-off in polar firn.
ISSN:0022-1430
1727-5652
DOI:10.1017/jog.2021.40