Ultrafast Spectroscopy and Watching a Reaction Happen · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Filming a reaction with light

Science · Chemistry · ages 23-24
Name ______________________   Date ____________

  1. A transient map shows a negative dip where the starting material absorbed. What is it?

    • The bleach
    • The product
    • Excited-state absorption

  2. What sets the shortest process a pump probe experiment can resolve?

    • The colour of the probe light
    • The duration of the pulses
    • The number of fitted models

  3. A fresh absorption that stays grown marks the product.

    Circle one:   True   False

  4. Two fresh absorptions appear: one fades in picoseconds, one stays. How do you assign them?

    • Both are products
    • Fading: product; staying: excited state
    • Fading: excited state; staying: product

  5. You fit a falling decay trace with a single exponential. What is the fit constant?

    • The pump energy
    • The peak height at zero delay
    • The lifetime under that model

  6. To resolve a faster step, you choose a shorter pulse.

    Circle one:   True   False

  7. A signal halves every 3 picoseconds and starts at 80 units. What does it read after 6 picoseconds? Type the number.

    Answer: ______________

  8. A feature grows in over two picoseconds and then decays. What does it imply for the mechanism?

    • An intermediate made, then used up
    • The bleach slowly recovering over time
    • The probe pulse arrived too early
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Filming a reaction with light W1-mt_wxQgetzzW5-s1

  1. The bleach · The lost absorption of the starting material shows up as the bleach dip.
  2. The duration of the pulses · Nothing briefer than the pulse width can be resolved.
  3. True · Staying signals are products, while fading ones are excited states.
  4. Fading: excited state; staying: product · Brief means excited state, while staying means product.
  5. The lifetime under that model · The fitted constant is the lifetime, and you name the model with it.
  6. True · Shorter pulses resolve faster motion.
  7. 20 · Two halvings apply: 80 to 40, then 40 to 20.
  8. An intermediate made, then used up · Rise then fall marks an intermediate tied to two mechanism steps.
Worksheet · LightMySky