Photon-burst method in high-resolution laser spectroscopy

Abstract

The sensitivity of high-resolution fluorescence spectroscopy has been enhanced by the detection of bursts of photons from single atoms crossing a laser beam. A tunable cw laser beam intersected a well-collimated atomic beam at right angles, and the fluorescent light was detected by an ellipsoidal collector and a photomultiplier.The passage of an atom through the beam was identified with a burst of detected photon pulses, which could be difkrentiated easily from the random background. For increasing burst multiplicity the spectra show improved background suppression and also significant peak narrowing. High-resolution spectra were obtained with as few as 10 atoms/sec crossing the laser beam. Statistical predictions for the case of transit-time limited signals are calculated and compared with results obtained for the Na 5890-A and Ba 5535-A transitions.

A Strategy for adoption of accelerator mass spectrometry by the earth sciences

“…A thirty-fold improvement in sample utilization has been obtained at low duty-cycle with a pulsed thermal-atom source (Fassett et al, 1984). Further selectivity (with some loss of sensitivity) could be obtained after mass analysis by observation of laserinduced resonance fluorescence of the ions or of neutralized atoms, detecting photon bursts from multiple excitation under conditions of small Doppler spread (Lewis et al, 1979).…”

Coincidence laser spectroscopy (CLS) for the detection of ions in ICP-MS (ICP-MS-CLS). A feasibility study

“…For example a 90 Sr + ion saturated at l = 421.671 nm (5p 2 P 1/2 -5s 2 S 1/2 ), A = 1.3 10 8 s À1 , at 5 keV will take 386 ns to pass through a detection volume 40 mm long and will produce B50 photons for detection during this period. This is the basis of the ''Photon Burst'' technique, as described by Fairbank 21,22 and others, 23,24 that employs the multiplicity of photon emission to discriminate against BG. The probability of detecting k events in a time t when the mean count rate is N s À1 is:…”

Laser spectroscopy on-line with nuclear accelerators

“…The introduction of the laser in this field has increased the sensitivity of purely optical experiments by several orders of magnitude and has even made possible the detection of single atoms. In suitable cases, coincidence or photonburst 3 techniques have, in addition, strongly reduced the background noise. It is, of course, the spectral purity, the excellent beam quality and the high power density of lasers that have made possible this dramatic improvement.…”