Laser-induced fluorescence of metastable xenon ions

Xenon ions in the metastable state 5d ⁴D_{$\text{7}\text{2}$} are excited by means of a tunable dye laser at 6051 Å. The excitation is monitored by non-resonant fluorescence at 5292 Å.     

Laser probing of ions confined in a cylindrical radiofrequency trap

We measure the lifetime of the 5 ²D_{$\text{5}\text{2}$} metastable level of Ba⁺ ions confined in a cylindrical radiofrequency trap as well as some parameters which characterize the confining properties of the trap. This is accomplished by studying the ion response to a short pulsed optical excitation saturating the 6 ²S_{$\text{1}\text{2}$}–6 ²P_{$\text{3}\text{2}$} transition.The measured lifetime of the 5 ²D_{$\text{5}\text{2}$} metastable level is 47 ± 16 s. The storage voltages for which the ion number shows a maximum are experimentally investigated. Their change when a light buffer gas is added is observed. The effect of this gas on the storage time is also specified.     

Resonant absorption in LiNdP4O12 lasers

The resonant loss in LiNdP₄O₁₂ (LNP) lasers has been investigated. The effective resonant loss coefficient for the 1.047(7) μm laser emission was measured to be 0.042 cm^-1. This value can be explained by resonant absorption due to the ⁴I_{1$\text{1}\text{2}$}→⁴F_{$\text{3}\text{2}$} transition including the reabsorption effect of the fluorescence resulting from the ⁴I_{$\text{9}\text{2}$}→⁴F_{$\text{3}\text{2}$} transition.     

Preferential excitation transfer in Cs1(6D32)- Cs(6S12) collisions

A cw dye laser beam, tuned near the Cs 8761 Å resonance (Cs¹(6P_{$\text{1}\text{2}$}) → Cs¹(6D_{$\text{3}\text{2}$}) transition) is focused into a Cs vapor. At a Cs density higher than 5 × 10¹⁵ cm^-3, we observe a greater 6P_{$\text{1}\text{2}$} population when the laser is on resonance than when it is off resonance. However, at a lower Cs density, the reverse is observed. This phenomenon is explained as due to the preferential excitation transfer process: Cs¹(6D_{$\text{3}\text{2}$}) + Cs(6S_{$\text{1}\text{2}$}) → Cs¹(6P) + Cs¹(6P), and the corresponding cross secti on is estimated to be (1.5^+1.5_-0.7) × 10^-14 cm² by fitting the experimental results to an approximate rate-equation analysis.     

Semi-leptonic decays of charmed mesons produced in γN collisions

We report here on a study of the characteristics of the semileptonic decay spectra from a pair of charmed hadrons produced via photoproduction. The inclusive production of charmed hadrons is phenomenologically parametrized as e^?aze^?bp_t2. Their decays are described by (i) decay of free charm quark in GIM, (ii) K¹ dominant mode, $\text{D}\text{→}\text{K}{}^1\text{l}\text{ν}$, and (iii) pure leptonic decays. We deduce that 〈M_eμ²〉 = 0.18 M_D² for free quark decay and 〈M_eμ²〉 = ?0.35 +-0.24 M_D² for K¹ dominant decay. For the specific purpose of the photoproduction experiment at FNAL whicc is currently searching for μe events, we incorporate the incident photon spectrum, and the decay distributions with and without the experimental acceptance criteria are presented.     

Pionic and radiative decay widths of charmed hadrons in a badly broken SU(4) symmetry

The width of ψ(4.414) is surprisingly small for a c$\text{c}$ state far above the charm threshold, Γ_exp ≈ 33 MeV. This fact can be qualitatively understood if one makes the conservative assignment 4 ³S₁. The nodes of the wave function reflect as zero's of the decay amplitude in the momentum of the decay products, and are responsible for the suppression of the couplings to the ground state charmed mesons, Γ(ψ(4.414)→D$\text{D}$+ D$\text{D}$¹ + $\text{D}$D¹ + D¹$\text{D}$¹ + F$\text{F}$ + F$\text{F}$¹ + $\text{F}$F¹ + F¹$\text{F}$¹) ≈ 15 MeV. All the modes are suppressed by factors of the order of 10³ with respect to the k³ spin counting prediction. The dominant modes are predicted to be D¹$\text{D}$¹, F$\text{F}$¹ + $\text{F}$F¹ and D$\text{D}$. Moreover, we show that the contributions from P-wave charmed mesons are reasonably expected to be suppressed either by phase space or by the nodes if their masses lie within certain range. We emphasize however that the smallness of the photon coupling remains to be understood.     

(6P-5D)-branching ratio in Ba II

Ba⁺ ions, confined in a r.f. quadrupole trap, were laser excited into the 6P_{$\text{3}\text{2}$} state. Observation of the decay into the metastable$\text{5D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{5D}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$ states yields the branching ratio

$\text{R =}\text{[I(6}\text{P}\text{3}\text{2}\text{? 5}\text{D}\text{5}\text{2}\text{)]}\text{[I(6}\text{P}\text{3}\text{2}\text{? 5}\text{D}\text{3}\text{2}\text{)]}\text{= 7.58 ± 0.57}$

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Collisional enhancement of the I(52P12) emission at 1.3μm by parent molecules CF3I,C2F5I,i-C3F7I and n-C3F7I

The magnetic dipole transition I(5²P_{$\text{1}\text{2}$}-5²P_{$\text{3}\text{2}$}) at 1.3152 μm is shown to be enhanced by collisions of the metastable iodine atoms with the parent RI molecules CF₃I, C₂F₅I, i-C₃F₇I and n-C₃F₇I. The enhancing mechanism is exciplex emission of the RI·I(5²P_{$\text{1}\text{2}$}) molecule at 1.3 μm, with different rates for each iodide. The influence of this effect on the measurement of the quantum yields to I(5²P_{$\text{1}\text{2}$}) and of the respective reaction rates by infrared fluorescence is discussed.     

Far infrared laser magnetic resonance spectrum of CH

Laser magnetic resonance spectra between 0 and 17 kG have been recorded and analyzed for $\text{(J′ ← J″) = (}\text{7}\text{2}\text{←}\text{5}\text{2}\text{)}$, $\text{(}\text{5}\text{2}\text{←}\text{3}\text{2}\text{)}$, and $\text{(}\text{3}\text{2}\text{←}\text{1}\text{2}\text{)}$ transitions in the CH molecule, using the optically pumped far infrared lasers: 118.8 μm (CH₃OH), 180.7 μm (CD₃OH), 554.4 μm (CH₂CF₂), 561.3 μm (DCOOD), and 567.9 μm (CH₂CHCl). Other transitions in CH were detected with the ¹³CH₃OH laser at 115.8, 149.3, and 203.6 μm. The CH radical was generated in a low-pressure methane and atomic fluorine flame within the laser cavity. Analysis of the M′_J ← M″_J structure yields wavenumbers for the rotational transitions mentioned above of 84.3494, 55.3397, and 17.8376 cm^?1, respectively. Combining results from the M_J analysis with the $\text{J =}\text{1}\text{2}\text{Λ-}\text{doubling}$ interval derived from radioastronomy measurements yields Λ-doubling values for the $\text{J =}\text{3}\text{2}\text{,}\text{5}\text{2}$, and $\text{7}\text{2}$ states of 0.0237, 0.1620, and 0.3759 cm^?1, respectively. Both the rotational intervals and the Λ-doublings are in good agreement with earlier less precise optical results. Analysis of the hyperfine structure yields values for the Frosch and Foley hyperfine parameters of a = +52, b = ?74, c = +52, and d = +43.6 MHz, in good agreement with recent ab initio estimates and radioastronomy measurements.     

Threshold of the 2ωpe instability in a laser produced plasma

$\text{3}\text{2}$ω_L emission from various plane targets irradiated by a 20 J, 5 ns neodymium laser pulse has been investigated. The onset of $\text{3}\text{2}$ω_L emission and an increase in intensity by five orders of magnitude is observed at a laser intensity of ≌2×10¹³W cm^-2, the threshold intensity predicted for excitation of the 2ω_pe instability.     

Subpicosecond photon echoes by using nanosecond laser pulses

Subpicosecond time resolutions have been obtained in photon echoes when a sample was excited by two nanosecond dye laser pulses with a smooth and broad spectrum. The dye laser was pumped by second harmonics of a Q-switched Nd:YAG laser, and the pulse width was 10 ns. The sample was 3% Nd³⁺-doped silicate glass, and the center frequency of the dye laser was tuned at 5910 Å on resonance with the ⁴I_{$\text{9}\text{2}$} ? ²G_{$\text{7}\text{2}$}, ⁴G_{$\text{5}\text{2}$} transition of Nd³⁺. The homogeneous transverse relaxation time T₂ was measured to be 91 ps at 10 K in agreement with the previous measurements by picosecond pulses.     

Determination of the atomic-state population in A Kr-Br2 mixture

The atomic-state populations of the 5s[1$\text{1}\text{2}$]° metastable level of Kr and of the 5s²P_{$\text{3}\text{2}$} resonant level of Br in a Kr-Br₂ mixture have been determined as functions of current strength. Occurrence of energy transfer from the Kr-level to the Br-level has been verified.     

Generation of 13.9 µm radiation from CO<Subscript>2</Subscript> by cascade lasing or externally applied CO<Subscript>2</Subscript> laser

13.9 μm radiation from the 10⁰0-01¹0 transition can be obtained from a CO₂ laser by saturating the 00⁰1-10⁰0, 10.6 μm transition with an internally generated q-switched pulse or by the application of an external 10.6 μm pulse. Because of Fermi resonance between the symmetric stretch and the bending modes, decay of population from the 10⁰0 level is fast, and such lasers operate at low power and energies. A theoretical model was developed to study such lasers. The results of the calculations indicate that a large-aperture E-beam-sustained discharge is effective for excitation of the cryogenically cooled gain medium, which uses He rich mixture at low pressure. The system is scalable and capable of generating large powers and energies.     

Kinetic investigation of the upper laser levels of the copper vapor laser

A modernized hook apparatus was used to study the population history of the ²P_{$\text{1}\text{2}$} and ²P_{$\text{3}\text{2}$} upper laser levels of the copper vapor laser. It was found that the effective lifetime of these levels is a sensitive function of the laser input current. The population of these levels saturates for a peak current of 200 A, which corresponds to a voltage slightly above the breakdown voltage of the tube.     

Relaxation of the 4G92 state of Nd3+ in LaCl3 and Nd3+ in La(Cl99.6Br0.4)3

The decay of the ⁴G_{$\text{9}\text{2}$} state of Nd³⁺ in LaCl₃ and La(Cl_99.6 Br_0.4)₃ was measured after pulsed laser excitation as a function of temperature. The decay rate is shown to depend besides the radiative transition on single-phonon relaxation between the states ⁴G_{$\text{9}\text{2}$} ($\text{μ =}\text{1}\text{2}$) and ⁴G_{$\text{9}\text{2}$} ($\text{μ =}\text{3}\text{2}$) and on multiphonon orbit-lattice relaxation from ⁴G_{$\text{9}\text{2}$} to ²G_{$\text{9}\text{2}$}. Partial substitution of Cl by Br only alters the radiative lifetime.     

Oscillator strengths of the first forbidden lines of rubidium

The oscillator strengths of the 5s-4d first forbidden lines of rubidium at 5165 Å were determined by performing CW tunable dye laser absorption measurements. Measured oscillator strengths of 8.06±0.48×10^-7 and 5.38±0.31×10^-7 for the ²D_{$\text{5}\text{2}$} and ²D_{$\text{3}\text{2}$} states, respectively, are compared with previously published values.     

Virtual effects of Higgs particles

The possibility of observing Higgs particles through virtual effects is considered in detail for a general gauge theory. The effect of charged Higgs particles on low-energy weak interaction processes, like muon decay, tau decay, nuclear beta decay, pion decay, and some higher-order processes is analyzed. The effect of flavor-changing neutral Higgs particles on rare decay modes of the muon and kaon, μe conversion, K^o-$\text{K}$^o and D^o-$\text{D}$^o mixing is also studied. We discuss constraints on possible extensions of the Weinberg-Salam model and experiments sensitive to their Higgs particles. In particular, we analyze the neutral Higgs which couple to fermions in the minimal SU(2)_L×SU(2)_R×U(1) model and find that they probably have mass greater than 100 GeV.     

Measurement of the fine structure splitting of the 32D multiplet of Li by stepwise excitation with cw dye lasers

The fine structure splitting of the 3²D multiplet of Li has been investigated using stepwise dye laser excitation of a strongly collimated atomic beam via the 2²P_{$\text{3}\text{2}$} level. The splitting is determined by a beat frequency measurement of two single mode dye lasers exciting the two 3²D levels. The result is Δν(3²D)=(1074±3) MHz.     

Two-photon optically pumped laser

At high temperature, the transmission peaks of a Fabry-Perot cavity filled with rubidium show sharp structures when the frequency of the laser is close to the 5S_{$\text{1}\text{2}$} - 5D_{$\text{5}\text{2}$} two-photon transition. These structures correspond to a laser emission between 5D_{$\text{5}\text{2}$} and 5P_{$\text{3}\text{2}$}. The wavelength of this laser emission (7759 Å) is smaller than the exciting wavelength (7779 Å).     

Stark effect investigation of highly excited 2D32 states in 133Cs utilizing a CW tunable dye laser

Stark effect measurements on the 8, 9 and 10 ²D_{$\text{3}\text{2}$} levels in ¹³³Cs were performed with the level crossing technique. The levels were populated using a two-step excitation, involving a tunable dye laser. The sign of the hyperfine constants could be determined.