Identification and atomization energies of gaseous molecules ScC2, ScC3, ScC4, ScC5, and ScC6 by high temperature mass spectrometry

Abstract

The high temperature Knudsen effusion mass spectrometric technique has been used to determine the thermodynamic properties of the gas phase species ScC2, ScC3, ScC4, ScC5, and ScC6, of which the second, fourth, and fifth are new molecules. The atomization energies Δ?a,0[ScC2(g)], ΔH°a,0[ScC3(g)], ΔH°a,0[ScC4(g)], ΔH°a,0[ScC5(g))] and ΔH°a,0[ScC6(g)] were obtained as 1185±14, 1779±22, 2455±22, 3139±29, and 3777±34 kJ mole−1 or 283.2±3.3, 425.2±5.3, 586.8±5.3, 750.2±6.9 and 902.7±8.1 kcal mole−1, respectively. The corresponding standard heats of formation ΔH°f,298 for gaseous ScC2, ScC3, ScC4, ScC5, and ScC6 were evaluated as 617±12, 735±20, 772±18, 798±24, and 874±28, kJ mole−1 or 147.5±2.9, 175.7±4.8, 184.5±4.3, 190.7±5.7, and 208.9±6.7, kcal mole−1, respectively. These results were derived from the enthalpies, ΔH°0, of the following reactions: The results for ScC2(g) and ScC4(g) are compared with the literature data. An upper limit for D°0(ScC)?440±21 kJ mole−1 was also obtained.