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.     

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.     

Measurements of the upper and lower level lifetime in He-Se lasers

The lifetimes τ₂ and τ₁ of the upper and lower levels of the 5227 Å (5p ⁴D_{$\text{7}\text{2}$}→5s ⁴P_5/2) laser transition in He-Se were measured. The obtained values are: τ₂=(18.5±1.85) × 10^-9 sec; τ₁=(2±0.4) × 10^-9 sec. The value of τ₂ was determined by measuring the time constant of the transient in the fluorescent emission consecutive to a sudden interruption of the laser oscillation inside the cavity.The value of τ₁ was determined by measuring the change induced by one laser transition on the unsaturated gain of another laser transition sharing the same lower level. Finally the “radiation trapping” factor is evaluated, thus ruling out the possibility that radiation trapping might be responsible for saturation in the laser output versus discharge current.     

Simultaneous cw laser oscillation on transitions of Cd+ and I+ in a hollow-cathode He-CdI2 discharge

Continuous-wave laser oscillation has been obtained on four transitions of Cd⁺ and eleven transitions of I⁺ using a hollow-cathode He-CdI₂ discharge as active medium. Laser output characteristics are similar for both Cd⁺ and I⁺ transitions, and simultaneous cw oscillation has been achieved at wavelengths ranging from blue (4416 Å Cd⁺) through green $\text{(}\text{5337}\text{5378}$ Å Cd⁺, 5407 Å I⁺), yellow $\text{(}\text{5678}\text{5761}$ Å I⁺) and orange (6127 Å I⁺) to red (6585 Å I⁺).     

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.     

Power limitations of the cw He-Hg laser

The variation of output power with discharge current in the hollow-cathode cw He-Hg laser has been investigated. In strong contrast to the comparable data for the positive-column discharge, the 6150 Å transition shows no turnover in output power with increasing current. Laser powers approaching 100 mW (cw) have been achieved at 6150 Å using a 3mm-bore, 50cm-long tube. Investigation of the excitation mechanisms for the 6150 and 7945 Å transitions confirms both are excited by thermal energy charge transfer reactions.     

Investigation of the metastable state of Na2[Fe(CN)5NO] · 2H2O by optical spectroscopy. II The electronic spectra of the ground and metastable states

The absorption spectra of Na₂[Fe(CN)₅NO] · 2H₂O were measured in the visible region in the range of 3400–7000 Å. In the metastable state, an additional absorption band in the long wavelength range is observed and the transition $\text{2}\text{b}{}_{\mathrm{<mtext>2</mtext>}}\text{(d}{}_{\mathrm{xy}}\text{)→}\text{7}\text{e(π}{}^1\text{?NO}\text{)}$ becomes weaker in the excited state indicating a population of the π¹(NO)-orbital. The laser excited emission spectrum shows a broad luminescence beginning at the excitation line $\text{λ =}\text{5145}\text{A}\text{?}\text{(}\text{19,436 cm}{}^{-1}\text{)}$ with a maximum at about 6250 Å (16,000 cm^-1). A strong sharp luminescence at about 7836 Å is registered and may be assigned to a transition 3b₁(d_x²?y²) or 5a₁(d_z²) to the antibonding π¹(NO)- orbital. Further the broad luminescence is superimposed by a series of sharp spikes. These sharp spikes can also be observed for several days, when the laser is switched off, and are depending on the crystal orientation.     

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.     

Microwave optical double resonance and fluorescence spectrum of NO2 excited by the 4579 Å line of the argon-ion laser

A microwave-optical double resonance (MODR) involving the $\text{J =}\text{21}\text{2}\text{←}\text{19}\text{2}$ and $\text{J =}\text{21}\text{2}\text{←}\text{17}\text{2}$ components of the 10_{0, 10} ← 9_{1, 9} rotational transition of the ground vibronic state of ¹⁴N¹⁶O₂ has been observed using the 4579 Å Ar⁺ laser line for excitation. By means of high resolution study of the laser excited fluorescence, the optical transition has been assigned to the $\text{J =}\text{19}\text{2}\text{←}\text{21}\text{2}$ spin component of the 9_{0, 9} ← 10_{0, 10} transition from the ground vibronic state to an unknown vibrational state of A₁ symmetry of the ²B₂ electronic state.     

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.     

Laser spectroscopy of FeO: Rotational analysis of some subbands of the orange system

Extensive laser excitation spectra and rotationally resolved laser-induced fluorescence spectra have been recorded for the “orange system” of gaseous FeO in the wavelength regions 5790–6140 and 5580–5640 Å. Detailed rotational analyses have been performed for about $\text{20}\text{Ω}\text{′}$ substates lying between 16 350 and 18 550 cm^?1. These are found to comprise a very severely perturbed ⁵Δ_i excited electronic state with a bond length of about 1.69 Å (which is responsible for the parallel polarization of the electronic transition from the ⁵Δ_i ground electronic state) and a large number of “extra” $\text{Ω}$ substates with B′ values ranging from 0.38 to 0.50 cm^?1, which almost certainly belong to high vibrational levels of lower-lying electronic states. Evidence about the natures of the “extra” states is confusing, however, with the ⁵⁴FeO⁵⁶FeO isotope shifts apparently being in conflict with the patterns of vibrationally resolved laser-induced fluorescence. Every single $\text{Ω}$ substate that has been analyzed shows rotational perturbations of varying severity. The density and magnitude of the rotational perturbations are quite exceptional for a diatomic molecule, and result in a new type of totally chaotic diatomic spectrum. There is a remarkable similarity to the visible spectrum of NO₂: in NO₂ the complications arise from the high density of perturbing ground state vibrational levels; in FeO there is a correspondingly high density of perturbing electronic states at lower energy. The great complexity of the FeO spectrum arises because the states are in an awkward intermediate spin-coupling case which still resembles Hund's case (a) but shows strong tendencies toward Hund's case (c) coupling.     

Distributions of i132 transfer strength in (τ, α)-induced population of odd-a platinum isotopes

The odd-A platinum isotopes ₇₈^{191, 193, 195, 197}pt have been populated by means of the (τ, α) reaction at E_τ = 50 MeV. Spectra covering a range of 4 MeV of excitation energy were obtained. Angular distributions for levels in this excitation range have been deduced. Only a few $\text{13}\text{2}{}^{\mathrm{+}}$ states are strongly populated in each isotope, the actual number being 1, 2, 3, and 2 for A = 191, 193, 195 and 197 respectively. The spacing between these peaks exhibits an interesting variation with neutron number. The data are compared with predictions of current quasiparticle-core coupling models.     

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).     

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.     

Laser spectroscopy investigation of the hyperfine structure of highly excited 2P32 states in alkali atoms

Highly excited ²P_{$\text{3}\text{2}$} levels in alkali atoms were populated using a multi-step excitation, involving a tunable dye laser. The hyperfine structure of the 9 ²P_{$\text{3}\text{2}$} level in ⁸⁷Rb and the 11, 12 ²P_{$\text{3}\text{2}$} levels in ¹³³Cs was determined with optical double resonance.     

Emission and laser-excitation spectra of the ≈A2Π ⇐ ≈X2Π transition of rotationally cooled bromochloroacetylene cation in the gas phase

Rotationally cooled bromochloroacetylene cations have been studied in the ≈X²Π_ω and ≈A²Π_ω (ω = $\text{3}\text{2}$, $\text{1}\text{2}$) states in the gas phase by two complementary spectroscopic techniques. The ≈A²Π ? ≈X²π band system was excited in emission by electron impact of a seeded supersonic helium free jet and as fluorescence by laser excitation of cations formed by Penning ionisation in a cooled environment. Comparison of the two sets of data locates the spin—orbit component bands and the origins of the systems, and allows the main spectral features to be vibronically assigned. The vibrational frequencies of most of the fundamentals are thus obtained to within ±2 cm^?1 for this cation in both the states.     

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.     

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.     

Fluorescence spectrum of chlorine dioxide induced by the 4765 Å argon-ion laser line

The fluorescence spectrum induced in ClO₂ by excitation with the 4765 Å argon-ion laser line has been studied under moderate resolution with the laser in single mode operation and under high resolution with the laser in multimode operation. The most intense features of the fluorescence have been assigned to excitation by the 23_{2, 22} ← 24_{2, 23} transition of the (0, 0, 0) ← (0, 0, 0) band of ³⁷ClO₂. Another set of features has been assigned to excitation by the 38_{0, 38} ← 37_{0, 37} transition of the (0, 0, 0) ← (0, 0, 0) band of ³⁷ClO₂.The vibrational structure and the ν₁ vibrational dependence of the rotational structure in the fluorescence have been least squares fitted giving a new set of vibrational constants and vibration-rotation interaction constants, $\text{α}{}_1{}^{\mathrm{B}}$ and $\text{α}{}_1{}^{\mathrm{C}}$.     

Investigation of the 3.46 MeV isomeric level of 38K with the 24Mg(16O,pnγ)38K reaction

The τ_{$\text{1}\text{2}$} = 22 μs isomeric level of ³⁸K at an excitation energy of 3458.0 ± 0.2keVf is strongly populated in the ²⁴Mg(¹⁶O, pnγ)³⁸K reaction. Delayed γ-rays are studied with Ge(Li), Si(Li), and NaI detectors. Accurate excitation energies, branching ratios and lifetimes of levels involved in the decay of the isomeric state are determined. The isomeric level predominantly decays by a dipole transition of 38.03±0.03 keV with a total conversion coefficient of α_T = 0.42 ± 0.15. Mean lives of ³⁸K levels are measured with the recoil-distance method. The results are τ_m = 10.1 ± 0.9 ps, 1.41 ± 0.14 ns and 101 ± 15 ps for the levels at excitation energies of 0.46, 2.65 and 3.42 MeV, respectively. It is suggested that the (1f_{$\text{7}\text{2}$})² structure of a low-lying J^π = 7⁺ state in combination with the selection rules for γ-decay in a self-conjugate nucleus is responsible for the isomerism.