R A M A N S P E C T R O S C O P Y O F T O L U E N E Answer the following questio

Question

R A M A N S P E C T R O S C O P Y O F T O L U E N E

Answer the following questions:

1. Calculate the scattered light wavelength where one expects to observe the Stokes shifted Raman peaks for the CH resonances (3000 cm-1). Use 785 nm as your Rayleigh wavelength. ( 4 pts )

2. Why are the low frequency modes more easily observed in the Raman than in the IR absorption spectra? ( 3 pts )

3. Consider that the monochromator used for the Raman experiement was set to EFF = 2 nm (at 785 nm), and the interferometer for the ATR-FTIR was set to 4 cm-1. Convert the EFF value for the Raman system into cm-1. (Note: this should give a reasonable value in the 1-50 cm-1 range. If you just convert 2 nm in cm-1 that gives a huge number. Instead you have to convert the range 785 nm to 787 nm to a range in cm-1 – it is a , not a ). Which system yielded a smaller effective bandwidth, the FTIR or the Raman system? ( 3 pts )

Explanation / Answer

1. Calculate the scattered light wavelength where one expects to observe the Stokes shifted Raman peaks for the CH resonances (3000 cm-1). Use 785 nm as your Rayleigh wavelength. ( 4 pts )

=10^7 nm/cm / 10^7 /495 - 3000 =   581.32 nm

=10^7 / 17202.020202=581.32 nm Stokes

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=10^7 nm/cm / 10^7 /495 + 3000 =  

=10^7 nm/cm/ 23202.02=430.99Anti-Stokes

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2. Why are the low frequency modes more easily observed in the Raman than in the IR absorption spectra? ( 3 pts )

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