Table 3a. Molecular Weights Associated With the Monoterpenes Detected by PTR-MS Compound m/z (mass + 1) Structure Description limonene 69, 81a, 82, 95, 96, 137, 138b C10H16H+, C6H9H+ monoterpene, fragments and isotopes 107c, 108, 123d*,124, 133, 151*, 152, 169*, 170 C10H16O2H+ uncalibrated oxidation product: limononaldehyde, fragments, and isotopes 139, 140 C9H14OH+ uncalibrated oxidation product: limonaketone and isotope 57, 69, 70, 71, 73, 75, 77, 83, 85, 87, 89, 93, 97, 99, 101, 103, 109, 111*, 113*, 115, 121, 125, 127, 129, 131, 135, 141*, 143, 149, 153, 155*, 156, 157, 165, 167, 171, 181, 183, 185, 187, 200d, 218d unidentified oxidation products myrcene 81, 82, 137, 138 C10H16H+, C6H9H+ monoterpene, fragments and isotopes 57, 64e, 65, 71, 73, 75, 77, 83, 85, 87, 89, 93, 97, 99, 101, 103, 111*, 113*, 115, 125, 127, 129, 139*, 141, 143, 145, 153, 155*, 159* unidentified oxidation products 3-carene 81, 82, 137, 138 C10H16H+, C6H9H+ monoterpene, fragments and isotopes 107, 108, 123*,124, 133, 151*, 152, 169*, 170 C10H16O2H+ uncalibrated oxidation product: caronaldehyde, fragments, and isotopes 71, 73, 75, 77, 79, 83, 85, 87, 89, 93, 94, 97, 99, 101, 103, 107, 109, 111, 113, 115, 121, 123*, 124, 125, 127, 129, 133, 135, 139*, 141*, 142, 151*, 153, 155*, 157, 167, 169*, 181, 183 unidentified oxidation products alpha-pinene 81, 82, 137, 138 C10H16H+, C6H9H+ monoterpene, fragments and isotopes 71, 72, 99, 107, 108, 109, 123*, 151, 152, 169, 170 f C10H16O2H+ uncalibrated oxidation product: pinonaldehyde, fragments, and isotopes 69, 73, 75, 83, 85, 87, 89, 94d, 97, 101, 103, 111*, 113*, 115, 121, 125, 127, 129, 131, 139, 141*, 153, 155*, 157, 165, 167, 171, 183, 185, 200e unidentified oxidation products aIons associated with parent terpenes listed in bold font represent ions > 20% of the unfragmented parent terpene. bAll monoterpenes occur predominantly on the parent m/z 137 and the fragment m/z 81 ions, with a small fraction (< 20%) occurring on the 13C isotope with m/z (138, 82). cUnidentified oxidation products in bold font are ions with > 5% yield (on a mole basis) from the parent terpene. dUnidentified oxidation products with asterisks represent ions that were observed in the canopy air of a coniferous forest in California by PTR-MS [Holzinger et al., 2005]. eEven mass-to-charge ratio oxidation products that are not carbon isotopes of other oxidation products are likely gas-phase nitrogen containing products, e.g., organic nitrates. fFragments were determined from correlations with m/z 151 (the dominant pinonaldehyde ion) that also agreed well with fragment ions reported elsewhere for pinonaldehyde [Wisthaler et al., 2001]. Additional fragment ions reported by Wisthaler et al. [2001], m/z 43 and 81, were excluded from the pinonaldehyde concentration due to interference by other compounds.