1) Take the derivative of this function to find the force function associated with it. 2) Demonstrate that for values of r close to re, the potential is close to harmonic: i.e., the force is proportional to displacement and opposite in direction. (Suggestion: expand the exponential function as a power series.) 3) Show that for large amplitudes, the vibrational frequency of the oscillator is less than the

Modern Physics
3rd Edition
ISBN:9781111794378
Author:Raymond A. Serway, Clement J. Moses, Curt A. Moyer
Publisher:Raymond A. Serway, Clement J. Moses, Curt A. Moyer
Chapter7: Tunneling Phenomena
Section: Chapter Questions
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and can you explain how you got the answer? It helps me understand the math 

1) Take the derivative of this function to find the force function associated with it.
2) Demonstrate that for values of r close to re, the potential is close to harmonic: i.e., the force
is proportional to displacement and opposite in direction. (Suggestion: expand the exponential
function as a power series.)
3) Show that for large amplitudes, the vibrational frequency of the oscillator is less than the
frequency of an equivalent harmonic oscillator. (Suggestion: include higher order terms in the
expansion.)
Transcribed Image Text:1) Take the derivative of this function to find the force function associated with it. 2) Demonstrate that for values of r close to re, the potential is close to harmonic: i.e., the force is proportional to displacement and opposite in direction. (Suggestion: expand the exponential function as a power series.) 3) Show that for large amplitudes, the vibrational frequency of the oscillator is less than the frequency of an equivalent harmonic oscillator. (Suggestion: include higher order terms in the expansion.)
The Morse potential
The harmonic potential, V(x) = ½kx?, is useful start for modelling molecular vibrations, but it has
limitations. A realistic potential between to atoms should accurately represent the sharp
increase in the potential as two nuclei come in close proximity, and also have the ability for a
bond to break: that is, an asymptote V →0 as x →00.
One option, as shown in the figure, is the Morse potential:
V(r) = D(1 – e-«(r=re))2
15
10
10
15
20
The parameter D is the well depth (or binding energy) of the potential, re is the bond length,
and a is the anharmonicity constant.
Transcribed Image Text:The Morse potential The harmonic potential, V(x) = ½kx?, is useful start for modelling molecular vibrations, but it has limitations. A realistic potential between to atoms should accurately represent the sharp increase in the potential as two nuclei come in close proximity, and also have the ability for a bond to break: that is, an asymptote V →0 as x →00. One option, as shown in the figure, is the Morse potential: V(r) = D(1 – e-«(r=re))2 15 10 10 15 20 The parameter D is the well depth (or binding energy) of the potential, re is the bond length, and a is the anharmonicity constant.
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