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Context. We perform a laboratory characterization in the 18-1893 GHz range and astronomical detection between 80-280 GHz in Orion-KL with IRAM-30 m of CH 2 CHCN (vinyl cyanide) in its ground and vibrationally excited states. Aims. Our aim is to improve the understanding of rotational spectra of vibrationally excited vinyl cyanide with new laboratory data and analysis. The laboratory results allow searching for these excited state transitions in the Orion-KL line survey. Furthermore, rotational lines of CH 2 CHCN contribute to the understanding of the physical and chemical properties of the cloud. Methods. Laboratory measurements of CH 2 CHCN made on several different frequency-modulated spectrometers were combined into a single broadband 50-1900 GHz spectrum and its assignment was confirmed by Stark modulation spectra recorded in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of vinyl cyanide detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. Results. Detailed characterization of laboratory spectra of CH 2 CHCN in nine different excited vibrational states: 11 = 1, 15 = 1, 11 = 2, 10 = 1 ⇔ ( 11 = 1, 15 = 1), 11 = 3/ 15 = 2/ 14 = 1, ( 11 = 1, 10 = 1) ⇔ ( 11 = 2, 15 = 1), 9 = 1, ( 11 = 1, 15 = 2) ⇔ ( 10 = 1, 15 = 1) ⇔ ( 11 = 1, 14 = 1), and 11 = 4 are determined, as well as the detection of transitions in the 11 = 2 and 11 = 3 states for the first time in Orion-KL and of those in the 10 = 1 ⇔ ( 11 = 1, 15 = 1) dyad of states for the first time in space. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature, which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The lowest energy vibrationally excited states of vinyl cyanide, such as 11 = 1 (at 328.5 K), 15 = 1 (at 478.6 K), 11 = 2 (at 657.8 K), the 10 = 1 ⇔ ( 11 = 1, 15 = 1) dyad (at 806.4/809.9 K), and 11 = 3 (at 987.9 K), are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. The vibrational temperatures derived for the 11 = 1, 11 = 2, and 15 = 1 states are 252 ± 76 K, 242 ± 121 K, and 227 ± 68 K, respectively; all of them are close to the mean kinetic temperature of the hot core component (210 K). The total column density of CH 2 CHCN in the ground state is (3.0 ± 0.9) × 10 15 cm −2 . We report the detection of methyl isocyanide (CH 3 NC) for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH 2 CHNC). We also give column density ratios between the cyanide and isocyanide isomers, obtaining a N(CH 3 NC)/N(CH 3 CN) ratio of 0.002. Conclusions. Laboratory characterization of many previously unassigned vibrationally excited states of vinyl cyanide ranging from microwave to THz frequencies allowed us to detect these molecular species in Orion-KL. Column density, rotational and vibrational temperatures for CH 2 CHCN in their ground and excited states, and the isotopolo...

A sensor based on rotational signatures in the submillimeter (SMM) region is described. This sensor uses frequency synthesis techniques in the region around 10 GHz, with nonlinear diode frequency multiplication to 210-270 GHz. This provides not only a nearly ideal instrument function, but also frequency control and agility that significantly enhance the performance of the spectrometer as a sensor. The SMM frequencies provide significantly stronger absorptions and broader spectroscopic coverage than lower-frequency microwave systems. Among the characteristics of the sensor are absolute specificity, low atmospheric clutter, good sensitivity, and near-term paths to systems that are both compact and very inexpensive.

Infrared and Raman spectra were recorded for the trans,trans (EE), cis,cis (ZZ), and cis,trans (ZE) isomers of 1,4-difluorobutadiene (DFBD). From these spectra and frequencies predicted from the adiabatic connection method, which is a hybrid of Hartree−Fock and density−functional theories, complete assignments of fundamentals were made for the observable s-trans configurations. The fundamentals for the trans,trans isomer are (in cm-1):  (ag) 3091, 3048, 1681, 1325, 1280, 1151, 1121, 409, 383; (au) 934, 798, 227, 154; (bg) 897, 830, 397; and (bu) 3086, 3056, 1638, 1299, 1221, 1088, 621, 133. The fundamentals for the cis,cis isomer are (in cm-1):  (ag) 3118, 3088, 1676, 1410, 1248, 1134, 946, 751, 232; (au) 914, 762, 330, 78; (bg) 897, 789, 580; and (bu) 3109, 3092, 1624, 1340, 1215, 1044, 632, 165. The fundamentals for the cis,trans isomer are (in cm-1):  (a‘) 3114, 3082, 3062, 3036, 1690, 1629, 1391, 1313, 1253, 1224, 1138, 1129, 1008, 706, 504, 308, 138; and (a‘ ‘) 929, 887, 824, 758, 526 (calculated), 230, 155. Overall agreement between the assignments and the predicted frequencies is quite good. With allowance for the difference between modes strongly dependent on CF or CCl motions, a very good correlation was found between the fundamentals of the three isomers of DFBD and the corresponding isomers of 1,4-dichlorobutadiene. Both sets of isomers are of special interest because they exhibit the cis effect, in which the cis,cis isomer has the lowest energy and the trans,trans isomer has the highest energy.

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