1. What is Rate of Intersystem Crossing (ISC)?

Definition: The rate of ISC is the rate of an isoenergetic radiationless process involving a transition between two electronic states with different spin multiplicity.

Purpose: This calculator helps determine the rate at which molecules transition from the singlet excited state to the triplet state.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \(\text{Rate}_{\text{ISC}}\) — Rate of intersystem crossing (mol/m³·s)
• \(K_{\text{ISC}}\) — Rate constant of intersystem crossing (Hz)
• \([M_{S1}]\) — Singlet state concentration (mol/m³)

Explanation: The rate is calculated by multiplying the rate constant by the concentration of molecules in the singlet excited state.

3. Importance of ISC Rate Calculation

Details: Understanding ISC rates is crucial in photochemistry, molecular spectroscopy, and the design of optoelectronic materials.

4. Using the Calculator

Tips: Enter the rate constant (K_ISC) in Hz and the singlet state concentration in mol/m³. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical value for K_ISC?
A: Typical values range from 10⁶ to 10¹² Hz depending on the molecule and conditions.

Q2: How is singlet state concentration determined?
A: It can be measured experimentally using absorption or fluorescence spectroscopy techniques.

Q3: What factors affect the ISC rate?
A: Molecular structure, solvent effects, temperature, and heavy atom presence can all influence ISC rates.

Q4: What's the difference between ISC and internal conversion?
A: ISC involves a change in spin multiplicity, while internal conversion occurs between states of the same multiplicity.

Q5: How does ISC relate to phosphorescence?
A: ISC populates the triplet state which can then decay via phosphorescence.