High-precision dual-inlet IRMS measurements of the stable isotopes of CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; and the N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O / CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; ratio from polar ice core samples
Atmospheric measurement techniques