# SpinDrops

> Interactive NMR spectroscopy simulator for understanding spin dynamics and pulse sequences. (iPhone/iPad app by Steffen Glaser.)

- Source: https://appshunter.io/ios/app/spindrops/id891357240 (this page in markdown: same URL + `.md`)
- Developer: [Steffen Glaser](https://appshunter.io/developer/857095959)
- Category: Education
- Price: Free
- Rating: 5.00/5 from 2 App Store ratings
- Age rating: 4+
- Requires: iOS 9.0 · 13 MB
- Languages: American English
- Released: 2014-07-17
- Data updated: 2026-06-10
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/spindrops/id891357240/reviews.md

## What is SpinDrops?

SpinDrops provides a novel approach to understanding magnetic resonance experiments and the underlying spin dynamics.  The app teaches fundamental concepts of modern NMR spectroscopy through numerous examples and an online tutorial.  The simple graphical interaction helps develop intuition of the mode of action and the design of pulse sequences.  Rich dynamics of spin systems (up to three coupled spins) can be explored interactively.  The app uses the DROPS representation to depict arbitrary spin states intuitively, yet also with theoretic rigor.  This representation is a generalization of the Bloch vector picture and provides a natural, one-to-one mapping between arbitrary spin states and so-called „droplets“.

Features of SpinDrops include:
- Customizable systems consisting of one, two or three spins 1/2.
- Arbitrary Initial states can be defined or chosen from predefined lists.
- Pulse sequences can be defined or selected from a list of pre-installed typical homonuclear and heteronuclear experiments, including individual 90° and 180° pulses, Hahn echoes, INEPT, DEPT, isotropic mixing, excitation of three-spin order and of multiple quantum coherence.
- Real-time simulations of spin dynamics can be interactively visualized using the graphical DROPS representation, which maps quantum mechanical operators to three-dimensional shapes based on spherical harmonics. This makes it possible to visualize abstract concepts such as anti-phase coherence, multiple-quantum order and coherence transfer.
- NMR signals (free induction decay, FID) can be acquired. The corresponding spectrum is displayed and can be interactively manipulated by changing the spin system parameters (frequencies and couplings), providing an intuitive approach to understand the multiplet structures of spectra and the differences between weak and strong couplings (roof effect).


Additional information can be found at www.spindrops.org:
- Extensive help is provided, including detailed tutorials, examples, challenges and information on the mathematical background of the DROPS visualization.
- Tutorials show how to define a desired initial state, how to create a new pulse sequence, and how to control the simulation and the graphical DROPS display. Furthermore, the properties of the DROPS visualization are explained and the interpretation of characteristic droplets is discussed. The shapes representing Cartesian product operators are discussed and it is shown how the coherence order of an operator is reflected in the shape and color of the corresponding droplet.
- Examples and challenges illustrate the interpretation of droplets, their symmetry properties, the evolution of single and coupled spins, the refocussing of offsets and couplings, spectral editing, and coherence transfer.

## Key features

- Interactive spin dynamics simulation
- Customizable spin systems (1-3 spins)
- Pulse sequence definition and selection
- Graphical DROPS representation
- Real-time visualization of abstract concepts
- NMR signal acquisition and spectral display


## Frequently asked questions about SpinDrops

### What is SpinDrops used for?

SpinDrops is used to understand magnetic resonance experiments and spin dynamics. It teaches fundamental concepts of modern NMR spectroscopy through interactive examples and visualizations.

### What kind of spin systems can SpinDrops simulate?

SpinDrops allows for customizable systems consisting of one, two, or three spins 1/2. You can define arbitrary initial states or choose from predefined lists.

### Can I create my own pulse sequences in SpinDrops?

Yes, you can define your own pulse sequences or select from a list of pre-installed typical homonuclear and heteronuclear experiments. This includes sequences like Hahn echoes, INEPT, and DEPT.

### How does SpinDrops visualize spin dynamics?

SpinDrops uses a graphical DROPS representation, which maps quantum mechanical operators to three-dimensional shapes. This visualization helps in understanding abstract concepts like anti-phase coherence and multiple-quantum order.

### Does SpinDrops offer offline play?

The provided description does not specify whether SpinDrops supports offline play. However, its nature as a simulation and educational tool suggests it may require an internet connection for certain features or updates.

### What is the update frequency for SpinDrops?

SpinDrops was last updated on July 15, 2020, with version 2.1.0. The frequency of updates is not explicitly stated, but this indicates it has received maintenance and improvements.

### Is SpinDrops suitable for beginners in NMR?

Yes, SpinDrops is designed to teach fundamental concepts of modern NMR spectroscopy through simple graphical interaction and numerous examples. It aims to develop intuition for pulse sequence design.

### What devices does SpinDrops support?

SpinDrops is supported on iPhone, iPad, and iPod devices, making it accessible to a wide range of Apple users interested in learning NMR.

## Version history (last 5 releases)

### 2.1.0 — 2020-07-15

Acquisition option in Pulse sequence editor with display of free induction decay (FID) and corresponding spectrum.
Option to optimize pulses.

### 2.0.4 — 2019-01-22

Updates and bug fixes, see spindrops.org/changelog.html for more info.

### 2.0.3 — 2018-06-21

Updates and bug fixes, see spindrops.org/changelog.html for more info.

### 2.0.0 — 2018-04-27

- The app has been rewritten to simulate spin dynamics based on the full density matrix formalism. This makes it possible to simulate not only ideal pulses but also the effects of resonance offsets and couplings during pulses. In addition,  strong coupling effects can be taken into account, both during delays and pulses.
- The density operator, as well as additional operators such as the Hamiltonian, effective Hamiltonian, and the effective propagator of a pulse sequence can be displayed 
(a) graphically using the DROPS representation,  (b) in terms of linear combinations of Cartesian product operators or other useful basis operators, and (c) in matrix form.
- In addition to the simplified and intuitive pulse sequences from SpinDrops 1.0, an alternative sequence language for advanced users is supported in SpinDrops 2.0, which makes it possible to copy and paste pulse sequences from the spectrometer, to define experiments directly in terms of Hamiltonians or propagators and to implement shaped pulses.
- Multiple workspaces let the user easily switch between multiple projects, e.g. for learning, teaching or research.
- Multiple concurrent phase cycle view demonstrates the mechanism of phase cycling.

The SpinDrops project has migrated to the Glaser Group at Technical University of Munich (TUM).

### 1.2.2 — 2015-05-28

The added display option „Parallax“ allows you to interactively change the perspective by tilting your device, which provides a more intuitive depth perception.

Bugfixes

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