DOI: 10.5061/dryad.v6wwpzh55
title: Data from: Ultrafast, all-optical coherence of molecular electron spins in room-temperature, water solution

description: The tunability and spatial precision of paramagnetic molecules makes them
 attractive for quantum sensing. However, usual microwave-based detection
 methods have poor temporal and spatial resolution, and optical methods
 compatible with room-temperature solutions have remained elusive. Here, we
 utilize pump-probe polarization spectroscopy to initialize and track
 electron spin coherence in a molecule. Designed to efficiently couple
 spins to light, aqueous K2IrCl6 enables detection of few-picosecond free
 induction decay at room temperature and micromolar concentrations.
 Viscosity is found to strongly vary decoherence lifetimes. This work
 redefines the meaning of room-temperature coherence by improving
 experimental time resolution by up to five orders of magnitude. Doing so
 unveils a new regime of electron spin coherence, opening the door to new
 synthetic design and applications of molecular quantum bits.
description: # Ultrafast, all-optical coherence of molecular electron spins in
 room-temperature, water solution
 [https://doi.org/10.5061/dryad.v6wwpzh55](https://doi.org/10.5061/dryad.v6wwpzh55) ## Description of the data and file structure In order to investigate ultrafast electron spin decoherence, five types of spectroscopy were used: pulse and continuous wave (CW) electron paramagnetic resonance (EPR), magnetic circular dichrosim (MCD), UV-Visible absorbance (UV-Vis), transient absorption (TA) and time-resolved Faraday ellipticity (TRFE), which was the main workhorse of the study. ### Files and variables Data is organised into 5 main folders, each corresponding to the different types of spectroscopy detailed above. Throughout all datasets, missing values are denoted with NaN. *EPR/* All EPR data saved in the Bruker .DSC / .DTA format, which can be read using the free EasySpin Matlab package: [https://easyspin.org/](https://easyspin.org/) The .DTA file contains the spectrum itself and is compressed, so not human-readable. The .DSC file is human-readable and contains relevant experimental parameters. *EPR/15KCWEPR/* Continuous wave EPR data collected at 15K and two microwave powers. CW spectra also saved as human-readable .txt file with columns for field in Gauss and intensity in arbitrary units. Filenames contain the name of compound, the type of measurement (X-band), microwave power, modulation amplitude (8 Gauss or "8GMA" for all), temperature (15K for all). Three scans were collected for an especially wide window of fields, denoted with the suffix "_wide". *EPR/PulseEPRdata/* Pulse EPR data in folders organized by experimental temperature. At each temperature Hahn-echo ("2pDecay"), Inversion Recovery ("InvRec") and Saturation Recovery ("SatRec") measurements were attempted. Not all of these were possible at higher temperatures due to the fast relaxation of the system. Filenames contain the name of the compound, the concentration and solvent (2mM in 60% water, 40% glycerol for all), Q for Q-band microwave energies, the temperature, the type of measurement (as in the previous paragraph) and the field strength the data were acquired at. *MCD/* The data are only for K2IrCl6 in H2O and the naming of each file gives the date, field orientation (parallel or antiparallel) and whether it is a sample or solvent. Sample MCD is found by taking the difference between parallel and antiparallel spectra and then between sample and solvent. *UV-Vis/* Each file is a .csv listing the wavelengths (nm) and corresponding absorbances. The first two columns, labelled "Baseline 100%T", show the transmittance from the solvent as a percentage at each wavelength. The second two, labelled "sample1", give the absorbance from the sample, corrected for the baseline, for each wavelength. The naming of each file gives the date, compound and solvent. *TA/* Each data file is named for its date, compound, solvent, pump wavelength and power and the probe supercontinuum used. Additionally, each experiment was repeated 5 times with repeat %i labelled accordingly with the suffix "_scan%i"; the average has no suffix. Each file is a .csv file with the first row listing the time-delays in ps and the first column wavelengths in nm. The remaining numbers show the absorbance change in OD at the corresponding time-delay and wavelength. *TRFE/* The four different solvents used are organized by subfolders. Each file is a .txt whose name gives the date of collection, the solvent condition ("e.g. flowin60:40H2Ogly" for flowing in a solvent mixture made up of 60% water and 40% glycerol), the type of measurement, pump polarization, chopper frequency and pump wavelength (TRFE, circular 338Hz and 512nm in all cases here), pump power, probe wavelength (400nm in all cases) and the field. Where necessary, decimal points are replaced by p, e.g. 1p3T for 1.3T. Within the file there are titled columns for the time-delay in ps, and the measured signal in Volts for each repeat and then the overall average. *TRFE/H2O/Power Dependence/* This subfolder contains further TRFE data used for calibration. There are several different pump powers (the lowest of which has been repeated [suffix "_2"] due to low signal-to-noise) and the files are labelled according the above convention. There is also a file containing the signal of pure water denoted by "justH2O" in the filename. ## Access information Data not publicly accessible elsewhere.