Analysis of the naphthalene vapour absorption bands at 3200 Å. II. Naphthalene d -8

Abstract

The absorption spectrum of octadeuteronaphthalene near 3200 Å has been measured and partially analyzed. The origin is at 32138.2 cm ^-1 , 118 cm ^-1 higher than that of naphthalene h -8. The analysis of the spectrum shows a nearly complete similarity to naphthalene h -8, with differences only in the relative ability of non-totally symmetrical vibrations to induce absorption along the shorter in-plane molecular axis. In naphthalene this ability is largely confined to two b _{3 g} vibrations of 438 cm ^-1 and 911 cm ^-1 in the upper state; in naphthalene d -8 the b _{3 g} vibration of 422 cm ^-1 behaves analogously to 438 cm ^-1 and induces the strongest bands in the system, but there are several higher b _{3 g} frequencies giving false origins, indicating important changes in the vibrational modes on deuteration. As in naphthalene, long-axis polarized bands show single maxima and short-axis polarized bands two maxima spaced by 2 to 3 cm ^-1 . The band group with principal head 490 cm ^-1 below the origin shows a structure unique in the whole system: it is proposed that this is due to Coriolis coupling of the a _g fundamental 493 cm ^-1 to a newly identified b _{3 g} fundamental 490 cm ^-1 . Several upper-state fundamentals are reported for the first time.