The energy of a Morse oscillator is calculated by the formula shown below.
E=hve(v+12)−hvexe(v+12)2 …(1)
Where,
• v is the vibrational quantum number.
• h is the Planck’s constant.
• xe is the anharmonicity constant.
• ve is the harmonic vibrational frequency.
The value of ve for HCl is 2989.74 cm−1.
The value of xeve for HCl is 52.05 cm−1.
Convert 2989.74 cm−1 to s−1.
2989.74 cm−1=2989.74 cm−1×2.9979×1010 cm s−1=8962.94×1010 s−1
Convert 52.05 cm−1 to s−1.
52.05 cm−1=52.05 cm−1×2.9979×1010 cm s−1=156.04×1010 s−1
Substitute v=0 in equation (1).
E=hve(0+12)−hvexe(0+12)2=12hve−14hvexe …(2)
Substitute v=1 in equation (1).
E=hve(1+12)−hvexe(1+12)2=32hve−94hvexe …(3)
Subtract equation (2) from equation (3).
ΔE(v=0→v=1)=(32hve−94hvexe)−(12hve−14hvexe)=hve−2hvexe …(4)
Substitute the value of Planck’s constant, ve and xeve in equation (4).
ΔE(v=0→v=1)=(6.626×10−34 J⋅s×8962.94×1010 s−1−2×6.626×10−34 J⋅s×156.04×1010 s−1)=59388.44×10−24 J−2067.84×10−24 J=5.732×10−20 J
The frequency of a transition in cm−1 is calculated by the formula shown below.
v=ΔEhc …(5)
Substitute the value of ΔE, Planck’s constant and speed of light in equation (5).
v=5.732×10−20 J6.626×10−34 J⋅s×2.9979×1010 cm s−1=2885.61 cm−1
Substitute v=2 in equation (1).
E=hve(2+12)−hvexe(2+12)2=52hve−254hvexe …(6)
Subtract equation (2) from equation (6).
ΔE(v=0→v=2)=(52hve−254hvexe)−(12hve−14hvexe)=2hve−6hvexe …(7)
Substitute the value of Planck’s constant, ve and xeve in equation (7).
ΔE(v=0→v=2)=(2×6.626×10−34 J⋅s×8962.94×1010 s−1−6×6.626×10−34 J⋅s×156.04×1010 s−1)=118776.88×10−24 J−6203.53×10−24 J=1.126×10−19 J
The frequency of a transition in cm−1 is calculated by the formula shown below.
v=ΔEhc …(8)
Substitute the value of ΔE, Planck’s constant and speed of light in equation (8).
v=1.126×10−19 J6.626×10−34 J⋅s×2.9979×1010 cm s−1=5668.52 cm−1
Substitute v=3 in equation (1).
E=hve(3+12)−hvexe(3+12)2=72hve−494hvexe …(9)
Subtract equation (2) from equation (9).
ΔE(v=0→v=3)=(72hve−494hvexe)−(12hve−14hvexe)=3hve−12hvexe …(10)
Substitute the value of Planck’s constant, ve and xeve in equation (10).
ΔE(v=0→v=3)=(3×6.626×10−34 J⋅s×8962.94×1010 s−1−12×6.626×10−34 J⋅s×156.04×1010 s−1)=178165.32×10−24 J−12407.05×10−24 J=1.657×10−19 J
The frequency of a transition in cm−1 is calculated by the formula shown below.
v=ΔEhc …(11)
Substitute the value of ΔE, Planck’s constant and speed of light in equation (11).
v=1.657×10−19 J6.626×10−34 J⋅s×2.9979×1010 cm s−1=8341.69 cm−1
Substitute v=4 in equation (1).
E=hve(4+12)−hvexe(4+12)2=92hve−814hvexe …(12)
Subtract equation (2) from equation (12).
ΔE(v=0→v=4)=(92hve−814hvexe)−(12hve−14hvexe)=4hve−20hvexe …(13)
Substitute the value of Planck’s constant, ve and xeve in equation (13).
ΔE(v=0→v=4)=(4×6.626×10−34 J⋅s×8962.94×1010 s−1−20×6.626×10−34 J⋅s×156.04×1010 s−1)=237553.76×10−24 J−20678.42×10−24 J=2.169×10−19 J
The frequency of a transition in cm−1 is calculated by the formula shown below.
v=ΔEhc …(14)
Substitute the value of ΔE, Planck’s constant and speed of light in equation (14).
v=2.169×10−19 J6.626×10−34 J⋅s×2.9979×1010 cm s−1=10919.20 cm−1
Substitute v=5 in equation (1).
E=hve(5+12)−hvexe(5+12)2=112hve−1214hvexe …(15)
Subtract equation (2) from equation (15).
ΔE(v=0→v=5)=(112hve−1214hvexe)−(12hve−14hvexe)=5hve−30hvexe …(16)
Substitute the value of Planck’s constant, ve and xeve in equation (16).
ΔE(v=0→v=5)=(5×6.626×10−34 J⋅s×8962.94×1010 s−1−30×6.626×10−34 J⋅s×156.04×1010 s−1)=296942.20×10−24 J−31017.63×10−24 J=2.659×10−19 J
The frequency of a transition in cm−1 is calculated by the formula shown below.
v=ΔEhc …(17)
Substitute the value of ΔE, Planck’s constant and speed of light in equation (17).
v=2.659×10−19 J6.626×10−34 J⋅s×2.9979×1010 cm s−1=13385.96 cm−1