Homonuclear diatomic molecules excited states

Hurley, A. C., Proc. Roy. Soc. [London) A216, 424, The molecular orbital theory of chemical valency. XIII. Orbital wave functions for excited states of a homonuclear diatomic molecule."... 

D N2) was determined as 9 79, 7 90, 7 42, 6 23, or 5-76 eV according to the assumed states of excitation of the nitrogen ion and the nitrogen atom produced. Spectroscopically obtained values for Z)(N2) are 9 76 or 7 38 eV, depending on the assumptions made. The retarding potential and appearance potential measurement alone is satisfactory for the interpretation of electron impact processes in homonuclear diatomic molecules, where there can be no doubt about the mass number of the ions. Possible confusion for heteronuclear diatomic molecules is not likely to be very great, but the method by itself is clearly inapplicable to dissociative ionization processes in polyatomic molecules, where the number of possible products is large. 

Curves for the negative-ion states of H2 and L are chosen to illustrate the procedures for the homonuclear diatomic molecules. Curves for benzene and naphthalene are examples of excited states for larger molecular negative ions. These illustrate the relationship between gas phase acidities and thermal electron attachment reactions. Such correlation procedures can be applied to systematic predictions for many different problems. 

The electron affinities of the main group homonuclear diatomic anions have been measured by PES. A few experimental values for the transition metal dimers are also available. The electron affinities of all the 3d homonuclear diatomic molecules have been calculated using density functional methods [1-4], Only the AEa of I2, 2.524 eV C2, 3.27 Si2, 2.2o S2, 1.67 F2, 3.0g Cl2, 2.4s Br2, 2.5, and 02, 1.07 have been measured by more than one method [1-3]. CURES-EC calculations confirm these to within 0.1 eV. Positive excited states Ea have been measured for 02, C2, and I2 and are inferred for other X2 [5-8]. Just as in the case of the atomic Ea, the trends in the Periodic Table can support the assignments of AEa for the other elements. 

Fig. AIII.2. Potential energy curves, electronic orbitals, and vibrational levels are schematically depicted for the electronic ground state and an excited electronic state of a homonuclear diatomic molecule such as Hg. The molecular c-axis is assumed to be perpendicular to the...

Fig. 8.9 (a) Illustration of the variables R, 0, and (p in the interaction potential V R,0,(p). (b) Schematic electron cloud distribution for excited homonuclear diatomic molecules in a 77 state. Also shown are the two directions of cp for a i7-type and a /7-type interaction potential... 

The small magnetic hfs in the E state of a homonuclear diatomic molecule is caused by the interaction of the nuclear spins / with the weak magnetic field produced by the rotation of the molecule. For the Nai molecular ground state the hyperfine splittings are smaller than the natural linewidth of the optical transitions. They could nevertheless be measured by the laser version of the Rabi technique [10.21]. A polarized argon laser beam at A, = 476.5 nm crosses the sodium beam and excites the Na2 molecules on the transition X = 0, 7" = 28) n (v = 3,7 = 27). The hfs... 

It would be instructive to illustrate the use of these rules. As a first example let us consider the core-hole excited states of homonuclear diatomic molecules. When one electron is removed from the core orbital, the original Da,h symmetry of the wavefunction is lowered to Coov This situation is depicted in the figure below where only the Is core electrons are represented. According to the rules in table 2, the Dooh group can be decomposed into two C v components related by a Ci or Cs operation. The two C >v structures (a) and (b) below ... 

For the homonuclear diatomic molecule Be2, give the MO configuration and bond order for the ground state and first excited state, based on the correlation diagram as the values of R approach (a) the separated atom limit and... 

Studies on molecular charge distributions and chemical binding due to Bader and co-workers include the first-row homonuclear diatomics (Bader et al., 1967a), the first-row diatomic hydrides (Bader et al., 1976b), the first-row 12- and 14-electron diatomic series (Bader and Bandrauk, 1968a), the second-row diatomic hydrides (Cade et al., 1969), and the excited, ionized, and electron-attached states of several diatomic molecules (Cade et al., 1971). Bader (1970, 1975,1981), Deb (1973), and Mulli-ken and Ermler (1977) review their works in some detail. 

Comparison of Formation of Homonuclear and Heteronuclear Alkali Metal Diatomic Molecules in Bound Excited States by PA... 

The principal reaction discussed above forms oxygen molecules in high vibrational levels of the ground state. This is chemi-excitation but is not chemiluminescence vibration-rotation transitions of homonuclear molecules are forbidden. For such cases electronic absorption spectroscopy is the required technique. For reactions in which a heteronuclear diatomic (or a polyatomic) molecule is excited these transitions are allowed. They are overtones of the molecular transitions that occur in the near infrared. These excited products emit spontaneously. The reactions are chemiluminescent, their emission spectra may be obtained and analyzed in order to deduce the detailed course of the reaction. 

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