The Bridge12 Q-Band resonator (B12TQLP) is optimized for pulsed dipolar EPR spectroscopy (e.g. DEER/PELDOR, SIFTER, RIDME, DQC, etc) in cases where the sample amount is limited. The resonator can be operated from 2 K to room-temperature and is compatible with standard cryostats such as the Oxford Instruments CF935 or the Cryogen Ltd. Cryogen-Free Cryostat. The resonator is connected to the spectrometer using a standard WR-28 waveguide coupling. For pulsed EPR experiments the coupling is adjusted using a micrometer screw, no frequency adjustments are necessary when changing the resonator coupling from critical to overcoupled.
The Bridge12 B12TQLP was designed with small samples in mind. The resonator accepts standard Q-Band sample tubes with an OD of 1.6 mm (e.g. Wilmad WG-221T-RB).
The sample is mounted on a sample stick for easy inserting of the sample into the resonator and removing, even if the sample needs to stay frozen at all times.
For accurate temperature readings a temperature sensor is mounted right next to the sample space. The sensor is compatible with many commercially available temperature controllers. Instead of relying on the cryostat temperature, this will give more accurate readings of the actual sample temperature.
Data courtesy of Dr. Alberto Collauto, PEPR Facility, Imperial College London, UK (Pmax = 300 W, 7 dB att., ~1 dB loss)
Using the micrometer screw on top of the resonator to adjust the iris position, the resonator can be completely overcoupled. Critically coupled, the B12TQLP has a loaded Q of ~ 400, corresponding to a bandwidth of 85 MHz. By changing the iris the resonator Q can be lowered to < 85, increasing the resonator bandwidth to > 400 MHz. The resonator coupling is designed with convenience in mind and the maximum bandwidth can be reliably achieved every time. Even at this low Q, the microwave conversion factor is > 5.1 G/sqrt(W).
Sample: BDPA/PS. Data courtesy of Prof. Song-I Han, UCSB, (Pmax = 300 W, tp(90) = 2 ns, 6 dB att., ~1 dB loss) LGRs are known for their large microwave conversion factors. The Bridge12 QLP resonator can achieve B1e field strengths of > 125 MHz, even when the resonator is completely overcoupled (bandwidth > 400 MHz). This will allow for 1H ESEEM/HYSCORE measurements and any experiment that requires hard microwave pulses.
Sample: MS57-2/o-Terphenyl, 65 K. The Bridge12 QLP resonator was developed for dipolar pulsed EPR experiments (DEER/PELDOR, DQC …). The resonators large excitation bandwidth and microwave conversion factor guarantees high sensitivity and results in short acquisition times (data analyzed using the SVD method, Madhur Srivastava (Cornell University) as described here).
… and large B1e Fields
Data courtesy of Prof. Song-I Han, UCSB 4-Pulse DEER/PELDOR Experiments
Sample: MS57-2/o-Terphenyl, 65 K.
Data courtesy of Prof. Song-I Han, UCSB
For DQC experiments, the entire EPR spectrum has to be excited. At Q-Band, the TEMPO spectrum has a widht of ~ 250 MHz. The Bridge12 QLP resonator is ideally suited for these type of experiments. With a bandwidth of > 400 MHz and a large microwave conversion factor the entire spectrum can be excited for DQC spectroscopy.
The Bridge12 QLP resonator was developed under a Small Business Innovation Research (SBIR) Grant by the National Institute of General Medical Sciencies (NIGMS) of the National Institutes of Health (NIH).
List of links to scientific publications in which the Bridge12 QLP resonator was used:
Below, find some general literature references for dipolar spectroscopy and the required instrumentation.