M. G. Payne

Direct counting of Xe atoms

Abstract Resonance ionization spectroscopy (RIS) is making possible direct counting of inert-gas atoms. Results for Xe are presented along with considerations involved in generalizing to other inert gases. Various applications of counters for inert-gas atoms are described.

Energy transfer from argon resonance states to nitrogen, hydrogen, and nitric oxide

Transfer of electronic energy from the resonance states Ar(1P1) and Ar(3P1) to diatomic nitrogen, hydrogen, and nitric oxide has been studied with a time‐resolved quenching technique. Rate constants for energy transfer were deduced from the changes of the rate of decay of excited states corresponding to known changes of the density of the diatomic molecules. For Ar*–N2 the rate constants were 5.4×10−11 and 0.8×10−11 molecule−1⋅cm3 sec−1 for Ar(1P1) and Ar(3P1), respectively. For Ar*–H2, the measured rate constants were 22×10−11 and 21×10−11 molecule−1 cm3 sec−1 for Ar(1P1) and Ar(3P1), repectively. The results for nitric oxide were 54×210−11 and 32×10−11 molecule−1 cm3 sec−1 for Ar(1P1) and Ar(3P1), respectively.

Optical power limiting of fullerenes

Optical power limiting processes in C60 solutions have been measured in a double‐pass geometry designed to produce high beam attenuation. Based on the concentration of C60 and measured attenuation of laser fluence, it was found that, at high intensities, more than 100 visible (532 nm) photons per C60 molecule can be absorbed during a single 7‐nanosecond laser pulse. The requisite features of such efficacious attenuation mechanisms are briefly discussed and a model meeting the requirements is described.

A sensitive, absolute, and time-resolved method for the study of reactive atoms

Abstract Laser techniques for the production of free atoms at time t = 0 and their detection at r > 0 have been developed to measure the diffusion of Cs atoms in Ar and the reaction of Cs with O 2 in Ar gas.

Studies of lifetimes of rotationally cooled NO2 using time-resolved fluorescence excitation spectra

Abstract A taunble, pulsed dye laser with output in the region of 5750 to 6000 A was used to excite rotationally cooled NO 2 which was produced by expansion in conjunction with argon carrier gas through a supersonic nozzle. The resulting time-resolved fluorescence excitation spectra were used the lifetimes of various vibronic bands of NO 2 ( 2 B 2 ). The lifetimes measured were in the region of 15 to 40 μs which were shorter than those obtained from cell experiments. For each individual excitation wavelength, only a single exponential decay was observed from very early times through 250 μs.

Suppression of electronic hyper-Raman emission by four-wave mixing interference

Abstract It is shown that an interference effect, involving parametric four-wave mixing, can almost totally suppress predicted examples of stimulated hyper-Raman emission in the direction of a laser pump beam, creating unidirectional backward stimulated hyper-Raman scattering. The effect is demonstrated in Na vapor.

Development of an atom buncher

An ‘‘atom buncher’’ for controlling the concentration of gaseous samples has been conceptualized, evaluated theoretically, fabricated, and tested with excellent results. In effect, the atom buncher greatly increases the probability that a free atom will be in a small detector volume at a desired time. This was accomplished by using cryogenic techniques to condense atoms on a small spot and a pulsed laser to momentarily heat the spot to release the atoms at the desired time. Our work on noble gas atom counting by using resonance ionization spectroscopy is discussed as one example of the applications of the atom buncher.

Effects of collective emission on multiphoton excitation and ionization near a three-photon resonance

Abstract We show that collective emission strongly affects excitation and the enhancement of multiphoton ionization near resonances involving odd numbers of photons. Such effects lead to striking shifts and broadening of resonantly enhanced multiphoton ionization signals near the odd photon resonance, and to a strong decrease in the ionization with increasing pressure.

Tunable VUV light generation for the low-level resonant ionization detection of krypton

High-power tunable VUV light pulses with energies up to 0.7 μJ were generated in the 115.7–116.9-nm region by use of a two-photon resonant four-wave mixing scheme in a Xe–Ar gas mixture. This is the highest reported pulse energy that has been produced in this wavelength region using a four-wave mixing process. Efficient detection of krypton isotopes at densities as low as 10 atoms/cm3 was demonstrated by resonantly ionizing the atom through its one-photon allowed state at the vacuum wavelength of 116.49 nm.

Saturated photodissociation of CsI

Abstract Every CsI molecule in a small volume was photodissociated with a laser pulse; a second pulsed laser detected each Cs atom through resonance ionization spectroscopy. Besides proving one-molecule detection, we obtained cross sections for photodissociation of CsI as a function of wavelength.