Vibrational Spectroscopy, L1

. . Vibrational Spectroscopy. L1.

. . Infrared Range. infrared spectrum Inm x-rays 1 pm gamma-rays -12 mg 1 mm micrmvaves 10S wavelenght Im radio short wave hard -10 ultra- violet soft 166 14.5 125 8.5 65 1 km wave 4.5 log wavelenght (m) log frequercy (Hz) visible spectum.

. . Which Molecules show IR spectra. Heteronuclear diatomic molecules like HCI, CO, NO etc. and.

. . How the dipole moment changes with vibration.

. . Molecular vibration can be modeled by balls attached by springs..

. . Symmetric stretching vibration at 3652 cm-1 O Anti-symmetric stretching vibration o at 2349 cm-1.

. . Different types of vibrational Modes present in a molecule.

. . TYPES OF VIBRATIONS Stretching Mode Symmetric In plane bending vibrations Scissoring Rocki ng Out plane bending vibrations Asymmetric Wagging 12 Twisting.

. . Stretching mode of vibration. Symmetric Stretching.

. . Bending Mode of Vibration. q p ox (Doxp q p Scissoring Twisting Rocking Wagging.

. . Frequency of vibration of a diatomic vibrator.

. . How the. vibrational. energy values. originate.

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. . Classical equation of vibration: Derivation. A B.

. . A B. m1 m2. re. x1 x2. f1 f2. Total displacement= x=(-x1)+x2=x2-x1 Applying Hook’s Law;.

. . x1=A1Cos(2π?t+?) x2=A2Cos(2π?t+?). Here A1 and A2 are the amplitudes, ? is the linear frequency and ? is the phase of the vibration. Thus the accelerations would be;.

. . On simplifying equations 1 and 2 we get. (K-4π2?2m1)A1=KA2 3.

. . Thus the frequency of the vibrating molecule is given as.

. . Thank you for patient hearing.