Xenon Molecules Research Articles

On xenon molecule excited state lifetimes

Time-resolved excitation spectra of xenon vapor in the 150 nm region are analysed in terms of four main fluorescence lifetimes corresponding to decays of four stable excited electronic states of the Xe dimer. The two shortest decay times, ≈ 2 ns and ≈ 60 ns, are assigned to the direct radiative relaxation of the two lowest excited ungerade states, ( 1Σ + u)0 + u and ( 3Σ + u))1 u respectively. The two longest decay times, ≈ 150 ns and ≈ 500 ns, must correspond to the overall depopulation rates of the two lowest excited gerade states, ( 3Σ + g)1g and ( 1Σ + g)0 + g, decaying into the gerade ground state by cascading down through the intermediate ungerade states.

The multiphoton ionization spectrum of xenon: Interatomic effects in multiphoton transitions

The multiphoton ionization spectrum of xenon was taken in the vicinity of the laser wavelengths corresponding to one-third the energy of transitions to the 5p5(2P3/2)6s, 5p5(2P1/2)6s, and 5p5(2P3/2)5d atomic levels. Many atomic resonances were observed, the most prominent being third photon resonances with atomic 5d levels and fourth photon resonances with atomic 4f levels. However, peaks corresponding to ionization through the 6s levels were weak or absent. Resonances in these regions showed extreme pressure dependence. At higher pressures (≳50 torr) a broadening of the atomic lines as well as the existence of continuum backgrounds and strong broad resonances peaking at the energy of transitions between excited states were seen. At low pressure (40 torr) the atomic lines were narrow and the broad peaks and background were no longer present. These high pressure features were interpreted to be a consequency of resonances with vibrational continua of excited state diatomic xenon molecules and illustrate the necessity of inclusion of molecular Franck–Condon factors into the multiphoton ionization probability of atomic gases at moderate pressures.

Problem of achieving population inversion in a short electric discharge in inert gases at high pressures

A theoretical analysis is made of the possibility of achieving a population inversion between the levels of bound and repulsive states of inert gas molecules under ionization conditions in a high-pressure electric discharge. A quasisteady electron energy distribution function is obtained. A study is made of the kinetics of the ionization discharge regime in inert gases and an estimate is obtained of the ultimate population inversion which may be achieved in a gas kept at a given pressure and subjected to a given electric field. Theoretical estimates of the ultimate population inversion and gain of bound-repulsive 3∑u+–1∑g+ transitions in xenon molecules are obtained under the conditions of self-sustaining and non-self-sustaining discharges.

Absorption bands of krypton and xenon molecules near the forbidden lines

Absorption bands of krypton and xenon molecules near the forbidden lines

Experimental investigation of the kinetics of formation of excited Xe2molecules in a compressed-xenon laser

The temperature dependences of the rate constants of the formation of excited xenon dimers and of the excitation quenching were determined. The experimental values of the rate constant of the three-particle formation of excited dimers were found to be described satisfactorily by the analytic dependence ln(β/β0) = 0.39×105T−2 + 0.66 (β010−32 cm6/sec; T was measured in °K). When the gas temperature was lowered from 295 to 149°K, the rate constant of the quenching of excited xenon atoms fell from α = (1.1±0.2)×10–13 cm3sec to α ~ 10–14 cm3sec. The measured radiative lifetime of the 3,1∑u+ state of the xenon molecule was found to be τ = 30±10 nsec.

A model for electron-beam excited VUV fluorescence from xenon

A model for the vacuum ultraviolet emission from electron-beam excited xenon dimers is proposed. The distinguishing feature of the model is its use of two different three-body formation ratesfor the singlet and triplet states of the xenon molecule which have spontaneous decat times of 4 nsec and 16 nsec respectively. Excelent agreement with experiment is found over a very wide range of pressures and currents.

Production Mechanisms and Radiative Lifetimes of Argon and Xenon Molecules Emitting in the Ultraviolet

Production Mechanisms and Radiative Lifetimes of Argon and Xenon Molecules Emitting in the Ultraviolet

Polarization free measurements of Rayleigh scattering of Lyman α

The authors study the scattering of Lyman alpha by hydrogen, nitrogen, argon, krypton and xenon. By using a calculated value for the Rayleigh scattering cross section for hydrogen, values for other gases are deduced. In the case of xenon it is found that the scattering is dominated by the formation of xenon molecules and a value of 17.1 Mbarn for this species is found.

High resolution spectrum of the xenon molecule in the vacuum ultraviolet region (1150–1300 Å)

The absorption spectrum of the Van der Waals dimer Xe 2 has been photographed in the region 1150–1130 Å with a ten-metre spectrograph. The vibronic analysis of twelve molecular systems provides information on the ground state and on several excited molecular states. Some of the numerous bands appearing in the Xe-rare-gas mixture spectra are examined and compared to those of Xe 2.

Crystal-field model study of the xenon hexafluoride molecule. II. Comparisons with other hexavalent xenon molecules

The two-electron crystal-field model previously used to describe in detail the energy levels of XeF6 is applied to other hexavalent xenon systems, namely the XeOF4, XeO2F2, and XeO3 molecules and the XeF82− ion. Comparisons of the calculated excited state energies of these three molecules at their observed geometries are made to those calculated for various geometries of XeF6. The strong low symmetry fields in XeOF4, XeO2F2, and XeO3 result in very high excitation energies, which may also be taken to represent greater energy stabilization for the lone electron pair relative to that for XeF6. The ground state energy of XeF82− is explored as a function of geometry, and within the two-space considered, the results match the structure observed in solid (NO)2XeF8.

De-excitation rates for excited xenon molecules

The time decay of the density of excited xenon molecules (Xe2*) in the lowest bound diatomic states was monitored by observing the photons (1730 ± 100 Å) emitted in transitions to the repulsive ground state. Mutual ionizing collisions of the excited diatomic states are responsible for the initial decay at high excited-state density. The measured rate for this process is (3.5 ± 1.4) × 10−10 cm3 sec−1. At lower excited-state densities, the decay of Xe2* is controlled by spontaneous emission [(20 ± 8) × 106 sec−1], collisional deactivation [(3,3 ± 1.3) × 10−18 cm2], and electronic recombination.

Excitation of vacuum ultraviolet emission from high-pressure xenon by relativistic electron beams

This letter reports an investigation of the vacuum ultraviolet emission from gaseous xenon excited with a 4-nsec 10-kA cm−2 electron beam. The observed decrease in the emission lifetime at 171.5 nm for high xenon number density is due to a quenching process intrinsic to xenon. Treatment of the quenching data yields a radiative lifetime of 130 ± 20 nsec for the excited xenon diatomic, and a quenching constant of 5.1 × 10−13 cm3 atom−1 sec−1. Thus, the theoretical threshold for laser action in excited diatomic xenon molecules is ∼ 26 times higher than had been previously anticipated from the 5-nsec lifetime observed in liquid xenon.

Absorption spectrum of the xenon molecule in the vacuum ultraviolet region

The observation of intense band systems attributable to Xe2 gives clear spectroscopic evidence of the formation of molecules even at low pressure.

Absorption Spectrum of the Argon Molecule in the Vacuum-uv Region

The absorption spectrum of diatomic argon has been investigated in the 780–1080-Å region with a 6.65-m normal incidence vacuum spectrograph using the helium and argon continua as background sources. Nine discrete band systems are identified. The present analysis shows that the ground state is stable, has a dissociation energy D00 = 76.9 cm−1, and six vibration levels, υ = 0–5. A number of previous calculations of intramolecular potentials agree with these experimental results. Definite dissociation products are assigned for some of the upper states of these systems. State designations, stabilities, and transitions from the ground state are discussed by analogy with an earlier study of the xenon molecule. In some of the upper states, the existence of potential humps (for which no definitive explanation is yet known) is demonstrated by the assignment of transitions to bound molecular states above the dissociation limits and by the onset of diffuseness in band progressions. The origin of the vacuum-uv argon emission continuum and of other emission features is discussed in relation with the observed absorption band systems.

Adsorption of Krypton and Xenon on Evaporated Metal Films

BRENNAN et al.1 quoted our earlier communication2 in connexion with the determination of the effective crosssectional areas of adsorbed xenon molecules, σ(Xe). However, a numerical error appears in their article. The values 13.8 and 17.2 A2 were not given in our communication and the value σ(Kr) = 19.5 A2 was not used as a reference value. Our communication indicated that we found from the measurements of xenon adsorption on evaporated nickel films at 78° K that σ(Xe) = 19.3 A2, and from measurements at 90° K that σ(Xe) = 21.8 A2. Moreover, σ(Kr) = 21 A2 was used as the reference value. The adsorbed amounts of xenon and krypton were always estimated by the same volumetric method and evaluated by means of the Brunauer–Emmett–Teller theory.