Reassignment of the electronic origin in the system of dibromocarbene

Single vibronic level emission spectroscopy of the system of dibromocarbene

“…In 1993, Xu and Harmony reported a detailed analysis of the spectrum under jet-cooled conditions using a pyrolysis source [55], and argued based upon the observed isotope shifts that the vibrational assignments of Zhou et al, were off by one quantum; the origin was therefore reassigned to $15 192 cm À1 . Recently, we have shown from an improved analysis of the excited state isotope shifts that both previous gas phase assignments are incorrect [50]; we reassigned the origin to $15 297 cm À1 , in good agreement with recent ab initio predictions [40,57].…”

“…Following the development of an improved discharge recipe for production of CBr 2 , and an extensive spectroscopic survey of theà 1 B 1 X 1 A 1 system that has led to a revision in the position of the origin [50] we have recorded SVL emission spectra of C 79 Br 81 Br and C 81 Br 2 which probe the vibrational structure of theX 1 A 1 state up to $7000 cm À1 above the vibrationless level. These spectra reveal many previously unassigned levels, and a nearly complete set of vibrational parameters was determined from a Dunham expansion fit.…”

“…Due to extensive interference from HCBr and Br 2 , emission spectra were only obtained for two bands, 2 12 0 and 2 13 0 (labels follow our revised assignment of the electronic origin) [50]. These authors reported that the pure bending progression (0, n, 0) did not appear in their emission spectrum, which is surprising given that: (1) this progression appears in the emission spectrum of every other triatomic carbene [16,20,21,49], (2) it was reported in the initial matrix emission studies of CBr 2 [51,52], and (3) a long bending progression is observed in the excitation spectrum of CBr 2 [53][54][55].…”

“…In this study, we report extensive single vibronic level (SVL) emission spectra of CBr 2 , obtained following the development of an improved discharge recipe for production of this carbene free from interference of CHBr or Br 2 [50]. We have recorded and rotationally analyzed the complete visible fluorescence excitation spectrum of CBr 2 , leading to a revision in the assignment of the electronic origin of this system [50].…”

“…We have recorded and rotationally analyzed the complete visible fluorescence excitation spectrum of CBr 2 , leading to a revision in the assignment of the electronic origin of this system [50]. For this work, we recorded emission spectra for both C 81 Br 2 and C 79 Br 81 Br isotopomers from a variety ofà 1 B 1 state levels.…”