dc.creator Jonas, D. M. en_US dc.creator Solina, Stephani Ann B. en_US dc.creator Rajaram, B. en_US dc.creator Silbey, R. J. en_US dc.creator Field, R. W. en_US dc.creator Yamanouchi, K. en_US dc.creator Tsuchiya, S. en_US dc.date.accessioned 2006-06-15T15:15:32Z dc.date.available 2006-06-15T15:15:32Z dc.date.issued 1992 en_US dc.identifier 1992-TE-03 en_US dc.identifier.uri http://hdl.handle.net/1811/12871 dc.description $^{1}$J.T. Hougen and J.K.G. Watson, Can.J.Phys., 43, 298 (1965). en_US dc.description Author Institution: Department of Chemistry and George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology; Department of Pure and Applied Sciences, The University of Tokyo en_US dc.description.abstract Nominally forbidden rotational transitions ($|\Delta K| \equiv |K^{\prime}-\ell ""|\leq 3$) have been observed in the stimulated Emission Pumping (SEP) spectra of acetylene in the $7000 cm^{-1}$ region of the $\bar{X}$ state via rotational-$\ell$- resonance in the $\bar{X}$ state and $axis-switching.^{1}$ It is significant to note that axis-switching, because the acetylene $\bar{A}\rightarrow\bar{X}$ transition is bent$\rightarrow$linear, allows access to new vibrational levels which would normally be dark solely due to rotational selection rules. From the rotational intensities observed in the $7000 cm^{-}1$ region of the $\bar{X}$ state a conservative estimate of the detectable range of SEP transitions in our setup, using 50$\mu$J of DUMP and a maximum observed fluorescence dip of 14\%, is 500 fold. Since fluorescence dips of 30\% are not uncommon, the practical range from the strongest to the weakest detectable SEP transitions is probably greater than 1000. The dynamic range of IR and Raman spectroscopy is typically smaller in congested regions accessible to SEP, IR and Raman. This unexpected dynamic range may be important for the reinterpretation of previous SEP spectra. For instance, in the case of acetylene, this unexpectedly large sensitivity range coupled with the newly discovered strong vibrational resonances may now reconcile the difference between the larger observed density of states at $15,000 cm{^{-}1}$ and the density of states calculated from a symmetry sorted direct anharmonic count. en_US dc.format.extent 198434 bytes dc.format.mimetype image/jpeg dc.language.iso English en_US dc.publisher Ohio State University en_US dc.title UNEXPECTED SENSITIVITY OF SEP: OBSERVATION OF FORBIDDEN TRANSITIONS IN ACETYLENE en_US dc.type article en_US
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