Detection of Vibrationally Excited Ethyl Cyanide in the Interstellar Medium

We have identified vibrationally excited CH 3 CH 2 CN (ethyl cyanide) for the first time in the interstellar medium. Using the Caltech Submillimeter Observatory, the Berkeley-Illinois-Maryland Association Array, and the Caltech Millimeter Array, we have detected several transitions from both the v b = 1 in-plane bending state and the v t = 1 torsional state in the Sgr B2(N-LMH) source. Because these excited states lie near 300 K above ground, vibrationally excited CH 3 CH 2 CN is potentially a useful probe of the hottest regions of dense, dusty molecular cloud cores where massive star formation is occurring. In addition, this identification will help account for many unidentified and misidentified spectral lines observed in hot molecular cores.