1. What is Observed Width at Half-Height in NMR?

Definition: The observed width at half-height (Δν_1/2) is the phenomenological linewidth of the resonance lineshape in NMR spectroscopy.

Purpose: It's a primary factor affecting both resolution and signal-to-noise ratio of NMR spectra.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \Delta\nu_{1/2} \) — Observed width at half-height (s^-1)
• \( T_2 \) — Transverse relaxation time (seconds)
• \( \pi \) — Archimedes' constant (~3.14159)

Explanation: The linewidth is inversely proportional to the transverse relaxation time, with π as the proportionality constant.

3. Importance of Linewidth Calculation

Details: Understanding linewidth helps in optimizing NMR experiments, interpreting spectra, and assessing sample quality.

4. Using the Calculator

Tips: Enter the transverse relaxation time (T₂) in seconds. The value must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What affects the transverse relaxation time (T₂)?
A: T₂ is affected by molecular motion, magnetic field inhomogeneity, and spin-spin interactions.

Q2: What's a typical T₂ value for liquids?
A: For small molecules in solution, T₂ is typically in the range of 0.1 to several seconds.

Q3: How does linewidth relate to spectral resolution?
A: Narrower linewidths (smaller Δν_1/2) result in better resolution of closely spaced peaks.

Q4: What causes line broadening in NMR spectra?
A: Factors include short T₂, magnetic field inhomogeneity, chemical exchange, and restricted molecular motion.

Q5: How can I measure T₂ experimentally?
A: T₂ can be measured using spin-echo experiments like the Carr-Purcell-Meiboom-Gill (CPMG) sequence.