New vibronic bands of the laser-vaporized C3 cluster. Determination of the ν3 fundamental in the Π state

Observation of New Bands in theA1Πu–X1Σg+Laser Induced Fluorescence Spectrum of C3

“…metric, the zero nuclear spin of 12 C means that half of the In this article we wish to report on the other bands observed rotational levels are missing due to nuclear spin statistics. in the ''hot'' spectrum, of which over 100 have not pre-For a S vibronic type given here of these ''odd'' symmetry bands are based on were also observed which may be distinguished from each the £ 3 assignment of Izuha and Yamanouchi (16) and define other by comparing the relative intensities of the first R and the energy positions of over 10 new levels in the A 1 P u state. P lines, corresponding to (R(1),P(1)) and (R(0),P(2)), A number of bands of both even and odd symmetry remain respectively.…”

“…The interest in these bending Jungen and Merer (15). Most recently, Izuha and Yamanoulevels arises from the fact that C 3 is floppy in its ground chi (16) have assigned the £ 3 fundamental in the A state in state, with a very low bending frequency of 63 cm 01 , and a careful LIF study using a vaporized graphite source. Their so it is an excellent test molecule for the study of large assignment gives a value of 541.7 cm 01 for the £ 3 fundamenamplitude motion.…”

Laser excitation spectrum of C3 in the region 26000–30700cm−1

“…It turns out that the progressions identified by other workers [4,15,16,19,[26][27][28][29] at lower energy can be extended fairly straight-forwardly to this high frequency region. There is initially very little stretch-bend anharmonicity, so that the intervals in the various bending progressions are almost independent of the number of stretching quanta excited.…”

“…Next, theà 1 P u state has a very large splitting between its two Born-Oppenheimer components, which provides beautiful examples of the effects of orbital angular momentum in a linear polyatomic molecule [4,14]. In addition, the antisymmetric stretching vibration of theà 1 P u state has a double minimum potential function, [15][16][17] while theà 1 P u -X 1 R þ g system (despite its perpendicular polarization) contains a vibronically-induced parallel transition moment [15,16].…”

“…Analysis of theà 1 P u state [4,15,16,19,[25][26][27][28][29][30][31][32] is complicated by the overlapping of many of the bands, the irregularity of the vibrational structure caused by the orbital angular momentum and the presence of rotational perturbations. When the 0 0 0-0 0 0 band of the 4050 Å system was found in spectra of the diffuse interstellar medium, [10] it was noticed [11] that the perturbations had resulted in a mis-assignment of the astrophysically-important R(0) line at 24676.7 cm À1 .…”