Effusing mass

Peck D-H, Miller M, and Hilpert K. Vaporization and thermodynamics of La j Ca,Cr03 investigated by Knudsen effusion mass spectrometry. Solid State Ionics 2001 143 391 400. 

Knudsen effusion mass spectrometry is used to measure the composition of the effusing beam (including the composition of the sample investigated, fragments or newly formed species) and in particular to determine the thermochemical data. The instrumentation is briefly described in Section 5.2.10.137... 

Compounds with Elements of Group V. An effusion-mass spectrometric study has afforded values of 380 + 20 and 450 + 20 kJ mol - respectively, for the dissociation energy and heat of formation at 298 K of CrN(g).59 X-Ray crystallographic data have been determined for TiCrAs and the metal-metal bonding in this and other NiAs-related structures has been discussed.60 The thermodynamic properties of... 

Later data on the vapor pressure of berkelium metal over the temperature range 1100-1500 K, obtained by using combined Knudsen effusion mass spectrometric and target collection techniques, have been published in 1982 (124). The vaporization equations obtained were... 

The most reliable values for the bond energies of the majority of these molecules have been obtained by using Knudsen effusion mass spectrometry ( ). For some of them, notably the alkali dimers, and Group IIA and Group IIB dimers, as well as for some of their intermetallic diatomic molecules, optical spectroscopic methods have provided the best or only determination of dissociation energies ( 3, ). 

The Knudsen effusion mass spectrometric method will be briefly described and Illustrated. The influence of various assumptions about the geometry and electronic structure of the molecules on the third law values of the reaction enthalpies obtained will be discussed. The development and use of empirical models for calculating dissociation and atomization energies will be Illustrated and their value as a bridge between experimental values and semi-empirical and theoretical calculations demonstrated. 

The examples given in this chapter illustrate the significance of recent experimental and theoretical molecular parameters on the reported dissociation energies that had previously been based on equilibrium measurements and on estimated molecular parameters. This additional information will permit the calculation of improved dissociation energies on the basis of the same experimental equilibrium data as typically obtained from Knudsen effusion mass spectrometry. 

Much theoretical work has been carried out on the lithium hydride molecule, which has become the workbench of the theoretical chemist (J ). Browne ( ), and Fraga and Ransil ( 3) have given the binding energy for the LiH ion by ab initio calculation Com-panion(j4) has applied the diatomic-in-molecule theory to the Li H and LiH. molecules and predicted the stabilities of these molecules. We have intensively studied the Li-H system by means of Knudsen effusion mass spectrometry, and identified all predicted molecules and ions as cited above(5), and reported the thermochemical properties of these gaseous species (, 2, ) ... 

Neubert, A. Ihle, H. R. Gingerich, K. A. "Thermodynamic Study of the Molecules BiLi and PbLi by Knudsen Effusion Mass Spectroscopy," J. Chem. Phys. 1978. 

We have developed several new measurement techniques ideally suited to such conditions. The first of these techniques is a High Pressure Sampling Mass Spectrometric method for the spatial and temporal analysis of flames containing inorganic additives (6, 7). The second method, known as Transpiration Mass Spectrometry (TMS) (8), allows for the analysis of bulk heterogeneous systems over a wide range of temperature, pressure and controlled gas composition. In addition, the now classical technique of Knudsen Effusion Mass Spectrometry (KMS) has been modified to allow external control of ambient gases in the reaction cell (9). Supplementary to these methods are the application, in our laboratory, of classical and novel optical spectroscopic methods for in situ measurement of temperature, flow and certain simple species concentration profiles (7). In combination, these measurement tools allow for a detailed fundamental examination of the vaporization and transport mechanisms of coal mineral components in a coal conversion or combustion environment. 

The primary experimental methods used in this study are the Knudsen Effusion Mass Spectrometric (KMS) and Transpiration Mass Spectrometric (TMS) methods, as described elsewhere [KMS, (9) ... 

Plante, E. R. "Vapor Pressure Measurements of Potassium Over K20-Si02 Solutions by a Knudsen Effusion Mass Spectrometric Method", 1979 p. 265, ibid, (8). 

Kerns = Knudsen effusion-mass spectrometry /Kete = Knudsen effusion-torsion effusion /tran = transpiration /Lang = Langmuir free evaporation /Lams = Langmuir-mass spectrometry... 

---