Discussion  Fr 27.01.2006 at 12:15,  HR30.1

Home work 11            Electronic Terms and Electronic Transitions
 

Exercise 1:       

a) One of the excited states of the C₂ molecule has the valence electron configuration 1σ²_g 2σ^*2_u 1p³_u 2p¹_g. Give the multiplicity and parity of the corresponding molecular term.

b) Explain the origin of the term symbol  ³Σ⁻_g for the ground state of O₂.

Exercise 2:   

a)   When light of wavelength 400 nm passes through 3.5 mm of a solution of an absorbing substance at a concentration 0.667 mmol  L^-1, the transmission is 65.5 per cent. Calculate the molar absorption coefficient of the solute at this wavelength and express the answer in cm² mol^-1.

 

Exercise 3:   

a)   The vibrational constant of O₂ molecule in its electronic ground state (X ³Σ⁻_g) is 1580 cm^-1, whereas that in the first excited state (B³Σ⁻_u) to which there is an allowed electronic transition, is 700 cm^-1. Having in mind that the energy separation between the minima of the potential energy curves of these two electronic states is 6.175 eV, calculate what is the wavenumber of the lowest energy radiative transition from the v=0 vibrational state of the electronic ground state to this excited state? Ignore any rotational structure and anharmonicity.      

b)  A certain molecule fluoresces at a wavelength of 400 nm with a half-time of 1.0 ns. It also phosphoresces at 500 nm. If the ratio of the transition probabilities for simulated emission for the S^* → S to the T → S transitions is 10⁵, what is the half-time of the phosphorescence?   

 

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