Related Experiment Video
Updated: Jan 28, 2026

A Protocol for Real-time 3D Single Particle Tracking
Published on: January 3, 2018
A differential rate meter for real-time peak tracking in optically detected magnetic resonance at low photon count
Kapildeb Ambal1, Robert D McMichael1
1National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Abstract:
We describe a real-time method to obtain normalized differential count rate signals from modulated systems with photon detection at single-photon count rates. The method is demonstrated with a real-time peak-locking and frequency control to track magnetic field using optically detected magnetic resonance of nitrogen-vacancy centers in diamond. This procedure allows us to measure the magnetic field continuously with a sensitivity of 4.1 µT/Hz1/2 and to track magnetic field sweep rates up to 50 µT/s. The differential rate meter automates the processing of voltage pulse outputs from the photon detector and provides noise levels on par with traditional photon counting methods using digital counters.
Related Concept Videos
The Integrated Rate Law: The Dependence of Concentration on Time
Reaction Rate
The mathematical representation of the change in the concentration of reactants and products, over time, is the rate...
Related Rates
Speciation Rates
Measuring Reaction Rates
Rate-Determining Steps
In a multistep reaction mechanism, one of the elementary steps progresses significantly slower than the others. This slowest step is called the rate-limiting step (or rate-determining step). A reaction cannot proceed faster than its slowest step, and hence, the rate-determining step limits the overall reaction rate.
The concept of rate-determining step can be understood from the analogy of a 4-lane freeway with a short-stretch of traffic-bottleneck caused due to...

