Can Isotopic Substitution Change a Bright State into a Dark State? The Case of thev3= 1 State of FClO3

✍ Scribed by F. Meguellati; G. Graner; K. Burczyk; H. Bürger

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 302 KB
• Volume: 185
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1997.7390

✦ Synopsis

High-resolution infrared spectra of monoisotopic samples of F 35 Cl 18 O 3 and F 37 Cl 18 O 3 have been recorded with the purpose of analyzing the n 3 fundamental at 535 cm 01 . However, this band could not be observed whereas it had been seen and studied earlier in F 35 Cl 16 O 3 . To determine the parameters of the £ 3 Å 1 state, indirect methods were used. Hot bands n n / n 3 0 n 3 (n Å 1 or 2) were first analyzed and their LSCD (Lower State Combination Differences) yielded rotational parameters of n 3 . Then, with the help of n 1 / n 3 , all rovibrational parameters of n 3 were obtained. Similar methods were applied to spectra of F 35 Cl 16 O 3 and F 37 Cl 16 O 3 to prove that the parameters of n 3 obtained in this fashion are identical to those determined directly for these isotopomers and are even more comprehensive. It is shown that the different character of n 3 in the two 18 O and in the two 16 O isotopomers is due to the fact that the former are much closer to a spherical top molecule ((A 0 0 B 0 )/A 0 Å 0.015). This is not only reflected in intensities different by two orders of magnitude but also in the very different values of a B 3 in these two pairs.