Interstellar Isomers: The Importance of Bonding Energy Differences

摘要: We present strong detections of methyl cyanide (CH3CN), vinyl (CH2CHCN), ethyl (CH3CH2CN), and cyanodiacetylene (HC4CN) molecules with the Green Bank Telescope (GBT) toward Sgr B2(N) molecular cloud. Attempts to detect corresponding isocyanide isomers were only successful in case (CH3NC) for its JK = 10-00 transition, which is first interstellar report this line. To determine spatial distribution CH3NC, we used archival Berkeley-Illinois-Maryland Association (BIMA) array data 4K-3K (K 0-3) transitions, but no emission was detected. From ab initio calculations, bonding energy difference between >8500 cm-1 (>12,000 K). Thus, cyanides are more stable would likely be formed preferentially over their counterparts. That CH3NC a single antenna (Gaussian beam size ΩB 1723 arcsec2) not an interferometer (ΩB 192 strongly suggests that has widespread region. Other investigators have shown CH3CN both LMH hot core surrounding medium, while appears deficient core. large-scale, nonthermal processes medium may account conversion core, dominated by thermal processes, does produce significant amount CH3NC. Ice analog experiments other radiation bombardment can thus supporting our observations. conclude separated such large differences distributed different environments, making evaluation column density ratios irrelevant unless it independently these species cospatial.