Investigation of the thermodynamic stability of the molecule LaIr(g) by high temperature mass spectrometry

摘要

The high temperature Knudsen effusion mass spectrometric technique has been used to identify the previously unkown molecule LaIr in the gas phase over the Landash;Irndash;Aundash;C(s) system. Evaluations of the enthalpy for the reaction LaIr(g) =La(g)+Ir(g) using the third and second law analysis yielded the following selected dissociation energy and standard heat of formation for the LaIr molecule.Ddeg;0(LaIr) =573plusmn;12 kJthinsp;molminus;1or 136plusmn;3 kcalthinsp;molminus;1,Ddeg;298(LaIr) =576plusmn;12 kJthinsp;molminus;1or 137plusmn;3 kcalthinsp;molminus;1, and Dgr;Hdeg;f,298(LaIr) =524plusmn;20 kJthinsp;molminus;1or 125plusmn;5 kcalthinsp;molminus;1. The dissociation energy of the gaseous molecule W2, which is isoelectronic with LaIr, is estimated to be 535plusmn;40 kJthinsp;molminus;1or 128plusmn;10 kcalthinsp;molminus;1.