Gas phase electronic spectrum of propadienylidene C3H2

Theoretical study of electronic absorption spectroscopy of propadienylidene molecule vis-â-vis the observed diffuse interstellar bands

“…The equilibrium geometry of the reference electronic ground state of l-C 3 H 2 is optimized at the Møller-Plesset perturbation level of theory employing second order (MP2) and fourth order (MP4) corrections and also by the B3LYP [32] method using the aug-cc-pVTZ basis set of Dunning [33]. The optimized equilibrium geometry parameters are given in Table 1 along with the available literature data [19,34,35]. It can be seen from the table that the geometry parameters agree well with the literature data.…”

“…The intense band between $200-300 Å region is attributed to the optically allowed e C 1 A 1 e X 1 A 1 transition in l-C 3 H 2 [6]. The gas phase measurement of the electronic absorption spectrum of l-C 3 H 2 was also attempted by cavity ring-down (CRD) spectroscopy [19]. This experiment was unsuccessful and a life-time of less than a picosecond of the e B state was envisaged for this failure.…”

Electronic spectra of linear HC5H and cumulene carbene H2C5

“…[11][12][13][14] Attempts to measure the 1 3 Σ − u ← X 3 Σ − g transition for the smallest members HC 3 H and HC 5 H in the gas phase failed so far. Whereas the two C 3 H 2 isomers with C 2v symmetry, which are more stable, were studied, [15][16][17][18][19] arguments were given for the non-observation of the electronic transition of HC 5 H, including low oscillator strength and unfavorable production conditions. 13 Several low-energy isomers of C 5 H 2 were investigated by quantum chemistry and microwave absorption spectrosa) Electronic mail: m.steglich@web.de b) Electronic mail: j.p.maier@unibas.ch copy.…”

Ground and low-lying excited states of propadienylidene (H2C=C=C:) obtained by negative ion photoelectron spectroscopy

“…[17][18][19][22][23][24] In addition to the fundamental chemical physics appeal, this particular band system has also been the source of a great deal of interest in the astrophysical community. As H 2 CCC is the simplest stable 84 cumulene carbene, a class of molecules that were postulated long ago 85 as potential carriers of DIBs, 86 it has attracted wide interest since its discovery in the diffuse interstellar medium.…”

“…They observed levels associated with the symmetry-forbiddenà 1 A 2 ←X 1 A 1 transition, but were initially unable to observe the stronger, symmetry-allowed B 1 B 1 ←X 1 A 1 transition because of the short lifetime of thẽ B 1 B 1 state. 22,23 Subsequently, they succeeded in measuring the prominent vibronic features of theB 1 B 1 ←X 1 A 1 transition at 4881 and 5450 Å, thus providing the basis for assigning these features in the DIB spectrum to propadienylidene. 24 Additional discussion of this topic is deferred to Sec.…”