What Does the Vibrational Mode Analysis Reveal About the Geometry of (NO)2+?

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SUMMARY

The discussion focuses on the vibrational mode analysis of the (NO)2+ ion, revealing key insights into its geometry. The analysis identifies one Raman active mode at 1450/cm, two strong IR active modes at 2400/cm and 550/cm, and one weak IR active mode at 3600/cm. The presence of four vibrational modes indicates that (NO)2+ is a linear ion, confirming its geometric structure as linear. The identified modes include symmetric stretch, asymmetric stretch, and symmetric bend, with the fourth mode remaining unidentified.

PREREQUISITES
  • Understanding of vibrational spectroscopy techniques, specifically Raman and IR spectroscopy.
  • Knowledge of molecular geometry and symmetry in linear molecules.
  • Familiarity with vibrational modes and their classifications (symmetric stretch, asymmetric stretch, bend).
  • Basic principles of molecular ion behavior, particularly in diatomic ions like (NO)2+.
NEXT STEPS
  • Research the principles of Raman spectroscopy and its applications in molecular analysis.
  • Study the characteristics of vibrational modes in linear molecules.
  • Explore the role of molecular symmetry in determining vibrational modes.
  • Investigate the significance of weak IR active modes in molecular spectroscopy.
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Chemistry students, molecular spectroscopists, and researchers interested in vibrational analysis and molecular geometry of ions.

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Homework Statement


For (NO)2+, experiments show 1 Raman active vibrational mode around 1450/cm; 2 strong IR active modes at 2400/cm and 550/cm; and 1 weak IR active mode around 3600/cm. What does that say about its geometry?




The Attempt at a Solution


Never mind, I think I got it :)
 
Last edited:
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Out of curiosity, what kind of mode does the weak IR active line correspond to?

The first 3 are clearly the symmetric stretch, asymmetric stretch and symmetric bend (in that order). That there are 4 modes suggests that the ion is linear, as indeed NO2^+ is. What is the fourth vibrational mode?
 

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