SINGLE PHOTON COUNTING FLUORESCENCE & FIELD SPECTROSCOPY & IMAGE APPARATUS

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The time-correlated single photon counting (TCSPC) fluorescence apparatus continues to perform as a state-of-the art spectroscopic instrument. In accord with the goal of developing new technologies out of existing instrumentation, a time resolved near-field optical spectrometer (TNOS), first developed at the RLBL within this year, revolutionizes the study of molecular dynamic and photonic processes by incorporating the extraordinary spatial resolution of the near field optical probe technique with state-of-the-art ultrafast spectroscopic methods. Our instrument is designed to acquire single location or scanned images of samples using three contrast mechanisms (force, intensity and excited state lifetime) in four, quickly converting, optical configurations. Current time domain spectroscopic resolution, determined by the application of time correlated single photon counting methods, is 20 picoseconds. Depending on the sample of interest, the RLBL-TNOS can be configured in the reflection or transmission geometry; and with each optical geometry, the near-field optical fiber probe can be implemented in illumination or collection mode. The multiplicity in contrast mechanisms and instrumental design versatility is to our knowledge unparalleled with existing near-field optical technology. Other developments include the separation of the conventional TCSPC system from the TNOS. This separation in detection and electronics, which will facilitate maximum use of both instruments, is nearly complete. A separate computer data acquisition center for the TCSPC is nearing completion. Frequency counting methods are also being incorporated into this system.