G.D. Watkins - Instrumentation

The major spectroscopic hardware within the lab is represented by three magnetic resonance spectrometers (14GHz, 20GHz and 35GHz). Optical excitation is provided by various lasers (one HeNe laser, one HeCd laser, two Ar³⁺ ion lasers, one CO₂ laser, one Nd-Yag laser and one Ti-Sapphire pumped laser) or incandescent, Xe/Hg-arc, and deuterium lamps. Optical detection is performed primarily by EG&G silicon diodes or North Coast germanium detectors. Lock-in detection and computer-assisted aquisition of data complete the spectroscopic chain. An annealing furnace and the Van der Graaff Accelerator serve to prepare the samples for study.

Spectrometers

Located in Room 102, this spectrometer uses a superconducting magnet. A wall-less design for the resonant cavity and quartz windows mounted on the cryostat allow 4-way access for direct optical excitation and detection. This is the only one (out of the three spectrometers) allowing also ODMR studies in absorption (MCDA-ODMR). In addition, OD-ENDOR experiments in luminescence and absorption are accessible by turning on an additional RF field.

This spectrometer (room 101) is also equipped for optical excitation and PL-ODMR detection. Here, optical excitation is carried via an optical fiber from room 102 and it is then thread through a quartz capillary tube that enters from the top of the cryostat and terminates just above the sample in the microwave cavity. The capillary tube, in turn, serves to channel the sample luminescence to an external detector. The distinctive feature of this spectrometer is that the cryostat can be transported into the Van der Graaff room and thus the unique in-situ irradiation experiments can be performed.

14 GHz

This spectrometer is a high sensitivity balanced bolometer system which can operate at controlled temperatures from 1.5 K (pumped liquid helium) to room temperature. It is currently used solely for conventional EPR and ENDOR spectroscopy. It is equipped for in situ application of uniaxial stress, and optical excitation is available through a light pipe.

Lasers