Experimental Studies of Allene, Methylacetylene, and the Propargyl Radical: Bond Dissociation Energies, Gas-Phase Acidities, and Ion-Molecule Chemistry

Construction of interstellar cumulenes and heterocumulenes: Mass Spectrometric Studies

“…The EA of CH 2 CC has been revisited by more recent photoelectron spectroscopic measurements: the ion was generated by the reaction of allene with O ÁÀ , as previously decribed (Robinson et al, 1995). Interestingly, this study also revealed a triplet excited state of the CH 2 CC diradical, which is some 30 kcal mol À1 more positive in energy than the singlet ground state.…”

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

“…27 25,26 Ions are collisionally cooled to approximately 300 K and can be further cooled with a liquid nitrogen jacket to obtain a "cold spectrum" of ions at ∼150 K. Anions are then mass-selected via a Wien velocity filter (m/ m ∼ 60).…”

“…25,26 Unlike conventional absorption spectroscopy, the selection rules in photoelectron spectroscopy offer the opportunity to probe a different group of electronics states (those that can formally be viewed in the molecular orbital picture as being obtained by a singleelectron removal from the anion − showed the origins for both the lowest singlet and triplet states, which exhibit a separation of 1.29 eV. 26 Although the measurements revealed complex spectral features located between the origins of the singlet and triplet manifolds, the photon energy was not high enough to access other excited states of H 2 CCC. In this paper, we report the photoelectron spectra of propadienylidene anion using several variants of photoelectron spectroscopy, [27][28][29] where the excited singlet and triplet states are observed as well.…”

“…6), which give T 0 = 1.2837 ± 0.0014 eV (10354 ± 11 cm −1 ). Beyond the term energy, however, no spectroscopic constants were determined in the work of Robinson et al, 26 although two weak features were observed and documented ∼300 and 1050 cm −1 above theã 3 B 1 origin. Both of these features are clearly seen in the SEVI experiment.…”

“…5) between eBE = 21 000 and 22 000 cm −1 is too broad to yield to meaningful analysis. The assignments involving theX 1 A 1 state are summarized in Table V, The earlier photoelectron spectrum 26 of theX 2 B 1 state of the propadienylidene anion revealed peaks at low eKE that have been attributed to the lowest triplet state. This lowest triplet predicted by ab initio calculations is theã 3 B 1 state.…”