Caltech Logo
Division of Chemistry and Chemical Engineering
Home  /  Research  /  Service Centers  /  Electron Paramagnetic Resonance (EPR) Facility

Electron Paramagnetic Resonance (EPR) Facility

The Caltech EPR facility is equipped with two Bruker EPR spectrometers, an EMX X-band continuous-wave (CW) EPR spectrometer, and a newly acquired Bruker ELEXSYS E580 pulse EPR spectrometer capable of pulse and CW EPR spectroscopy at both X and Q-bands, as well as a variety of electron-electron double resonance (ELDOR) and electron-nuclear double resonance (ENDOR) spectroscopies. Groups or research laboratories interested in using instrumentation in the facility are welcome to visit the laboratory in the sub-basement of Crellin Hall (B264) or email Paul Oyala at phoyala@caltech.edu.

Facility Access

In order to comply with division guidelines for safely reopening facilities, please observe the updated instructions on how to access the EPR Facility.

In the initial phase of reopening, access to facility lab spaces are restricted to only the facility manager (Paul Oyala) and GLA (Dirk Schild). The facility manager will run all samples, as many as possible within a 24 hour turnaround period (for CW-EPR at 77 K or room temperature only) during weekdays between 9 AM and 6 PM.

  • A station for contact-free sample drop off will be set up just outside of Crellin B264, where clearly labeled frozen EPR samples can be left in a LN2 storage dewar with 6 separate sample containers.
  • Samples should be labeled with a 1 inch section of lab tape wrapped tightly around the sample and stuck to itself, with sample identity written in permanent marker.
  • Any caps or rubber septa must be removed after freezing, before putting the sample in the LN2 dewar (even airtight caps often let in LN2 when submerged, creating a potential explosive device when the sample is removed and warmed even slightly). 
  • Use of J. Young tubes (or other gas-tight fittings) with this new system is generally discouraged, but if absolutely necessary for experimental reasons, a tall LN2 dewar will be provided at the drop-off station which has a tested hold time of ~ 12 hours - make sure that the valve itself is never submerged in LN2.
  • Notice of sample drop-off and all relevant sample details should be emailed to the facility manager, as well as desired experiments.
  • Data files will be emailed back to the user once experiments have been completed.
  • Time sensitive samples (e.g. room temperature reaction monitoring) or other specialized experiments that will not fit within the sample drop off system will require consultation with the facility manager for a set time during which the user can access the CW EPR lab space after sanitation of all work surfaces.

Facility Instrumentation

EPR Sample Guide

Bruker_ELEXSYS_E580

Scheduling sign-up

Located in a renovated lab in the sub-basement of Crellin (B264), this instrument is a state-of-the-art Pulse and CW EPR spectrometer from Bruker capable of CW EPR, Pulse EPR, and ELDOR and ENDOR experiments at both X- and Q-Bands (9 GHz and 34 GHz, respectively). Additionally, it is equipped with an Arbitrary Waveform Generator (AWG) integrated into the pulse-forming unit which is capable of generating shaped pulses for advanced pulse EPR applications at either operating frequency.

  • Magnet
    • 10" Bruker EPR Magnet
  • Bridges
    • X-Band Pulse/CW E580 Bridge
      • SPFU Pulse Forming Unit
      • Spin Jet-AWG for ELDOR experiments (multiple MW frequency experiments) and generation of both frequency and amplitude shaped pulses. User-defined pulse shapes can be imported as well.
      • DICE ENDOR Unit
    • Q-Band SuperQ-FT Bridge
      • 10 W power upgrade for π/2 pulses of ≈ 10 ns.
  • Cavities/Resonators
    • X-Band
      • MS-5 Pulse EPR/CW EPR resonator (5 mm max sample diameter)
      • MD-4 Pulse EPR/ENDOR Dielectric Resonator (4 mm max sample diameter)
    • Q-Band
      • D-2 Pulse EPR/ENDOR Dielectric Resonator (1.8 mm max sample diameter)
  • Temperature Control
    • ColdEdge Variable temperature cryogen-free cryostat system
      • Capable of operation with stable sample temperatures as low as 5.4 K.
      • Uses a helium compressor and GM cryocooler to cool the sample space without the need for liquid helium or nitrogen as coolant.
      • Only consumes ~ 15 L of helium gas per thermal cycle for purging sample space.

Bruker_EMX_Xband_CW_EPR

Scheduling sign-up

Located in the basement of Crellin in B160, this instrument is an X-band CW EPR spectrometer capable of CW experiments from cryogenic temperatures to room temperature.

  • Magnet
    • 14" Bruker EPR Magnet
  • Bridges
    • X-Band CW Bridge
  • Cavities/Resonators
    • X-Band
      • High Sensitivity Cavity – 4119HS-W1
      • Cylindrical-mode resonator room temp EPR on aqueous or high-dielectric samples.
  • Temperature Control
    • Oxford ESR 900 liquid helium/nitrogen flow-through cryostat
    • Liquid nitrogen immersion dewar for experiments at fixed temperature at 77 K
    • Room temperature EPR – aqueous samples or high dielectric samples may be measured if small diameter capillary tube is used.

FY2019 EPR Facility Rates

FY2021 CCE Rate Sheet (Effective 10-1-2020)

Contact Information

Paul Oyala, Ph.D.
Office: B250A Crellin
Labs: B264, B160 Crellin
Telephone – Office: (626) 395-4885
Lab: (626) 395-6055
Email: phoyala@caltech.edu

Mailing Address

Caltech
Chemistry 164-30
1200 East California Blvd.
Pasadena, CA 91125