Physics 780.04 Winter Quarter 2007 Dr. Herbst 14 February MIDTERM EXAMINATION (100 POINTS) IN CLASS 1. (20 points) Consider a spectral transition between two non-degenerate states separated by 1000 cm-1 . The Einstein A coefficient for the transition is 1 s-1 . In absorption, the spectral line is broadened by pressure broadening with a FWHM Δν of 100 MHz. Determine the absorption coefficient (cm-1 ) at resonance and calculate the fraction of incident radiation that traverses 1-cm and 1-m cells at this wave number. The concentration of molecules in the lower state is 10 15 cm-3 . 2. (15 points) The electron affinity of atomic hydrogen is 0.76 eV. This statement means that the negative ion H-has its ground state 0.76 eV below that of H(1s) + e. Find the shielding that each electron must exert upon the other in H-so that the simple independent electron model reproduces the experimental electron affinity. 3.
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