Vapor phase, electronic spectra

The bonding in metal hexacarbonyls and hexacyanides is described in terms of molecular orbitals. Vapor phase electronic spectra for the metal hexacarbonyls are reported in the range 35(X)-1700 k. A molecular orbital energy level scheme is presented which is able to account for the observed d-d and charge-transfer absorption bands in the d met complexes. The charge-transfer transitions all are assigned as metal (d) to ligand (v ). 

In the commonly used electron-impact (El) mode, a mass spectrometer bombards molecules in the vapor phase with a high-energy electron beam and records the result of electron impact as a spectrum of positive ions separated on the basis of mass/charge (m/z) most of these ions are singly charged. The mass spectrum of... 

Electronic Spectra of d6 Metal Hexacarbonyls and Hexacyanides. A. Metal Hexacarbonyls-—The electronic spectrum of Cr(CO)6 in the vapor phase shows two intense absorption bands at 35,780 and 44,480... 

In the solid state, the phenyl nuclei of biphenyl are coplanar (Dhar, 1932 Kitaigorodsky, 1946 Rizvi and Trotter, 1961). Bastiansen (1949) reports that the angle between the rings is 45° in the gas phase as determined by electron diffraction. The conformation of biphenyl in solution is not established (Wheland, 1955). It has been argued to be coplanar on the basis of the Kerr constant (Chau et al., 1959). Recent observations of the electronic spectrum of biphenyl and certain derivatives in the solid, liquid, and vapor states were interpreted as indicative of a 20° deviation from coplanarity in solution (Suzuki, 1959). 

Tellurium-oxygen system comprises a wide number of phases. Tellmium monoxide TeO probably exists only in the gas phase. No evidence of its existence in the solid state has been obtained. The He(I) photoelectron spectrum of the molecular beam that has been formed by heating Te02 in vacuo indicates that TeO is the dominant species in the vapor phase.Studies of the absorption and emission spectra of TeO(g) have yielded the bond dissosiation energy of263.2kJmoU. The Te=0 bond length of 1.828 A. is estimated from the rotational fine structme of the electronic absorption spectrum. 

Since an electronically-excited molecule can make a transition to several different vibrational states, and since, in addition, changes in rotational energy occur, the electronic spectrum of a molecule will involve a series of bands. If the electronic spectrum is observed in the vapor phase, the bands will consist of a series of sharp lines, which result from the closely-spaced rotational levels (see Figure 2.4). These sharp lines are known as the fine structure of the bands. In the liquid state or in solution the molecules cannot rotate freely. In these states the fine structure is considerably blurred. 

In the vapor-phase spectrum the next electronic transition is found as a set of three bands at 205.4, 199.5, and 193.9 nm equidistant on a frequency scale (spacing >1445 cm ). These bands are assigned (26b) to the first member of a Rydberg series showing vibrational fine structure. A further absorption Is observed at 175 nm (22) and at 160 nm (26, 27). In -heptane solution the Rydberg transition seems to be obscured by the appearance of an absorption maximum at 190 nm, superimposed on the slope of a lower lying absorption band, possibly the same as the one at 175 nm In the gas-phase spectrum. 

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