Two resonances in the photodetachment spectrum of H, one just below the n = 3 threshold and the other just below the n =4 threshold, were observed decaying into H {n'=2)+e. The n =3 resonance shows a preference for the n'=2 channel when compared with total-detachment measurements. Fanoline-shape fits give central energies of 12.652+0.003 eV for H * (3) and 13.338+0.004 eV for H **(4). These values are in good agreement with current theoretical calculations. PACS number(s): 32.80.Fb, 31.50.+w, 32.80.Cy
Laser photodetachment on a relativistic H beam has revealed several series of resonances in which both electrons are excited. These "bound states in the continuum" appear as dips in the partial production cross sections of various excited states of neutral hydrogen. We present here a detailed account of the experimental observation of the resonances and the results of fits of the measured yields to sets of Fano profiles. A simple analytic formula for the energy-level spacing in this quantum-mechanical three-body system is verified.In this paper we report the observation of several series of high-lying 'P resonances in the photodetachment cross section of H . The energy levels of these doubly excited states are shown to obey a simple and elegant analytic formula. We discuss here in greater depth the results presented earlier. '
Multiphoton detachment from H ~ has been studied using linearly polarized light for photon energies from 0.15 to 0.39 eV. Characteristic threshold structures were observed. The electron detachment rates are estimated at peak laser intensities from 2 to 12 GW/cm 2 in the laboratory frame. The two-photon detachment data reveal intensity-dependent shifts of the H ~ electron detachment threshold energy.PACS numbers: 33.80.Rv, 33.80.Eh Multiphoton detachment (MPD) from H ~ provides a window on fundamental multiphoton physics. 1 Structures in the continuum 2 far above the detachment threshold need not be considered for moderate laser fields. Because high-power lasers have had limited wavelength tunability, with the exception of the measurements using relativistic Doppler shifts, the general behavior of the MPD rate (cross section) versus photon energy has been explored only in theory. 3 Comparisons between theory and experiment involving multiphoton ionization (MPI) of neutral atoms are usually complicated by intensity-induced shifts, resonances, and the laser intensity distribution. In addition, subtle gauge problems 4 call for experimental data. Thus, it is desirable to study a simple system like H ~, using a tunable laser, to obtain an unobstructed view of MPI processes.The first observation of MPD in H ~ was reported recently. 5 However, 6 difficulties precluded detailed data analysis. Here, we report new observations of MPD of H "~ in moderate laser fields. These data reveal clear threshold phenomena occurring near photon energies where a transition from one order of absorption to another can take place (e.g., N-photon absorption to 7V + 1). Double-electron detachment from H ~~ was not observed. Briefly, 5 ' 6 an 800-MeV beam of H ", at the Los Alamos Clinton P. Anderson Meson Physics Facility (LAMPF), was made to intersect with a focused CO2 laser beam. The H ~ beam, roughly 3 mm in diameter, consisted of 0.25-ns micropulses, with a separation of 5 ns. A transversely excited atmospheric CO2 oscillator-amplifier, including a low-pressure gain cell in the oscillator, was operated in the TEMoo, single-axial mode with wavelength of 10.6 //m. Linearly polarized, temporally smooth laser pulses had a duration of -130 ns, full width at half maximum (FWHM), and a l-/is long tail. The measured intensity distribution in the focal region of a 25.4-cm focal-length lens demonstrated that the beam was nearly diffraction limited. The beam diameter at the focus was 110 ± 5 jjm (FWHM), corresponding to a transit time of 0.24 ps in the ion's frame when the beams cross at 90°, and a Rayleigh range of 2.6 mm. The highest peak laser intensity in the experiment was estimated to be 12 GW/cm 2 (±10%) in the laboratory frame. The photon energy (iTiab) was Doppler shifted to Zs c . m . in the center-of-mass (cm.) frame of the H ~ ion according to £c.m. -yO +j8cosa)£ , i ab ,where a is the angle of intersection (a =0 when head on) and p (0.842) and 7 (1.85) are the usual relativistic parameters. The photon-energy spread in the ion's frame i...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.