Ritz assignment and Watson fits of the high-resolution ring-puckering spectrum of oxetane

✍ Scribed by Giovanni Moruzzi; Marc Kunzmann; Brenda P. Winnewisser; Manfred Winnewisser

• Book ID: 104151773
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 782 KB
• Volume: 219
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1016/s0022-2852(03)00021-3

✦ Synopsis

Oxetane is a four-membered ring molecule exhibiting a large-amplitude ring-puckering motion. In order to analyze this vibration we recorded a rotationally resolved far-infrared spectrum between 50 and 145 cm À1 . The analysis of the ring-puckering fundamental band with the assignment of 1108 lines, has been presented in a previous paper. In the present work we present a list of further 6531 assigned transitions between the five lowest excited ring-puckering states. The 4983 term values involved in the transitions assigned in this and in the preceding work have been evaluated by the ''Ritz'' program, and are now available. An A-reduced Watson Hamiltonian in any of the three representations I r , II r , and III r was used to perform a fit of the assigned transitions. Precise rotational constants and quartic as well as a full set of sextic centrifugal distortion constants were obtained for the investigated ringpuckering states. For the first time, high-resolution values for the vibrational G v parameters have been obtained, and we have added terms in x 6 and x 8 to the double minimum-potential well describing the ring-puckering motion, in order to reproduce their values within the experimental accuracy. The same potential still reproduces the lower resolution values of the Q-branch origins involving higher ring-puckering states up to v rp ¼ 14 found in the previous literature.