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In this study, the B1Π excited state of NaH has been experimentally studied for the first time. Pulsed laser-induced fluorescence excitation spectroscopy was used to investigate the B1Π electronic state of NaH. A total of 48 ro-vibronic transitions were observed, including within the B-X (0-0) and B-X (0-1) transition bands. Only one B-state vibrational level was identified, and a series of PQR lines, with eight e-parity and eight f-parity sublevels (v' = 0, J' = 1-8), were assigned. The level assignment was supported by a comparison of the experimental line positions with the ab initio calculations, the dispersed laser-induced fluorescence spectrum of the NaH B1Π → X1∑+ emission, and the V-type optical-optical double resonance spectra. The Dunham-type coefficients, the mean internuclear distance, the harmonic vibrational frequency ω, and the dissociation energies D0 and De of the B1Π state were determined.

We present a 445-nm InGaN blue diode laser in wavelength-tunable Littrow-type external cavity with a single longitudinal mode output, and a linewidth of 4.7 MHz. Its tuning range was estimated at 4 nm. The maximum output power was up to 20 mW, and the slope efficiency was approximately 0.36 W/A. The external cavity-diode laser linewidth was measured as 4.7 MHz with a lasing threshold to 8.1 MHz at higher applied current. The slope of the linewidth broadening with applied currents was calculated as 57 kHz/mA. And the wavelength tuning range was approximately 4.3 nm at low applied current and narrowed to approximately 2.6 nm at high applied current. A blue external cavity diode laser can deliver a single frequency beam within entire operation range.

The mode evolution of an InGaN blue laser diode with operating current and diode temperature was investigated. The spectra of a 445-nm InGaN blue laser diode with operating currents and diode temperatures was recorded using an ultrahigh resolution spectrometer and a scanning Fabry-Perot interferometer. The blue laser diode can deliver a mW-level single frequency beam with about 20 MHz linewidth at nearly above the lasing threshold. And the temperature-dependent wavelength drift was estimated as 0.31 nm for single longitudinal mode operation region. The spectra showed the number of the longitudinal modes increased with raising operating current. Analysis of the mode evolution of a blue laser diode with operating current and diode temperature is important when how to choose the laser diode for specific applications.

The effect of polarization on the ladder-type electromagnetically induced transparency (EIT) spectra of

The 2

The effect of polarization on the ladder-type electromagnetically induced transparency (EIT) spectra of 133Cs atoms at room temperature for the transitions 62P1/2-62P3/2-112S1/2 is experimentally studied. The entire spectra with additional peaks arising from the Doppler effect are observed. As the relative angle between the probe’s and coupling’s plane of polarization arranges at 0°, 45°, and 90°, the peak height ratio of 44′3" to 44′4" increases by more than 7 times with corresponding values of 0.19, 0.69, and 1.4. Meanwhile, that of 45′4" to 44′4" are found to be 0.61, 0.87, and 1.23 (doubled), respectively. A theoretical model built to explain the experimental results with the considerations of optical pumping effect, two-photon transition probability, dephasing rate, and integration all over the velocity distribution. The simulation and experimental results are well-agreed.

We report the saturation spectroscopy of carbon dioxide inside a hollow glass waveguide (GW) using a tunable mid-infrared difference frequency generation (DFG) source. This DFG source was generated in a periodically poled lithium niobate crystal with a tuning range from 3.97 to 4. 71 μ m . Saturated spectroscopy was performed on the R(60) transition of CO 2 0001 ← 0000 band at 4. 2 μ m inside a hollow GW of diameter 300 μ m and length 1 m. The saturation dip signal was found with a pump power as low as 0.18 mW inside the hollow GW. The linewidth of the dip was determined to be 4.40 MHz.

Vibrational levels (v = 6-42) of the NaH C

In the young and active tectonic belt of southwestern Taiwan, reconstructed stratigraphy in the distal part of the foreland basin reveals at least two regional unconformities with the younger ones covering the areas farther from the mountain belt. In contrast with the previously proposed monotonous basin development, the temporal–spatial distribution of the unconformities indicates the back-and-forth migration of the foreland basin margin. Three distinct episodes of rapid subsidence during the foreland basin development have also been identified. The onset of the basin development can be well constrained by the initial rapid subsidence at 4.4–4.2 Ma, which happened only in the proximal part of the basin. This was followed by two younger episodes of rapid subsidence events at 2–1.8 Ma and 0.45 Ma, which were encountered initially in the areas progressively farther from the orogenic belt. We propose a model of episodic tectonic evolution in the distal part of the foreland basin in southwestern Taiwan. During each episode of rapid subsidence, uplifting that corresponds to the forebulge began with a concurrent rapid subsidence in the areas closer to the basin center and was followed by rapid subsidence and deposition of widespread strata onlapping toward the basin margin. Part of the widespread strata and its overlying deposits would be eroded in the beginning of the next episode when the forebulge shifted toward the orogenic belt. In general, rate of forebulge migrating away from the orogenic belt during the early stage was slower than that derived from a previously proposed kinematic model of a steady migration of the orogenic belt. This might be due to a rifted and weaker lithosphere beneath the foreland basin. Once the foreland basin migrated onto the less stretched lithosphere, the basin would expand rapidly into the craton.

The 2 1Π state of NaH has been observed up to the last bound vibrational level using pulsed optical-optical double resonance fluorescence depletion spectroscopy. A total of 20 rovibrational energy levels (v = 2–4 and J = 1–9) were assigned to this electronic state by means of comparing the successive rovibrational spectra to the eigenvalues of the ab initio potential energy curve. The decrease of background fluorescence near the atomic asymptotic limit Na(3d) + H(1s) is an indication of reaching the dissociation limit of the NaH 2 1Π state. Unobserved rovibrational levels (v = 0 and 1) are due to poor Franck-Condon overlap of 2 1Π ← A 1Σ+ transition within the accessible rovibrational levels of intermediate A 1Σ+ state of this work.

Previous studies have shown that Cordyceps militaris (CM) has a hypoglycemic effect, but the actual mechanism remains unclear. This study explored the hypoglycemic mechanism of aqueous extracts of CM in normal Wistar rats. First, the optimal dose of CM for lowering plasma glucose and insulin secretion was tested. Further, atropine and hemicholinium-3 (HC-3) were injected and a western blot was used to investigate insulin signaling. It was found that 10 mg/kg CM extracts had a stronger hypoglycemic effect than a higher dose (100 mg/kg); therefore, a dose of 10 mg/kg was used in subsequent experiments. In normal rats, CM extracts decreased plasma glucose by 21.0% and induced additional insulin secretion by 54.5% after 30 min. When atropine or HC-3 was injected, CM induced a hypoglycemic effect, but the enhancement of insulin secretion was blocked. By western blotting, significant increases in the insulin receptor substrate 1 (IRS-1) and glucose transporter 4 (GLUT-4) were observed after CM feeding. However, the elevation of these signaling proteins was abolished by atropine or HC-3. Taken together, these findings indicate that CM can lower plasma glucose via the stimulation of insulin secretion and cholinergic activation involved in the hypoglycemic mechanism of normal Wistar rats. Copyright © 2012 John Wiley & Sons, Ltd.

Doppler-free two-photon transitions of cesium 6S1/2→7D3/2, 5/2 were observed in a thermal stabilized cell. A repeated spectrum of 75 MHz introduced from the side band of an electro-optical modulator served as a frequency marker to improve the accuracy of frequency measurement. The hyperfine magnetic dipole constant A and electrical quadrupole constant B of Cs 7D3/2, 5/2 can be derived from the splitting intervals of the observed spectra. The results are: A=7.36(07) MHz, B=−0.88(87) MHz for the 7D3/2 state, and A=−1.81(05) MHz, B=1.01(1.06) MHz for the 7D5/2 state. These coefficients are improvements for testing high-precision measurements and determining fundamental physical constants.

The outer well of the NaH C 1 Σ + excited state was determined using pulsed optical–optical double resonance fluorescence depletion spectroscopy. The level-selected fluorescence of the A 1 Σ + state is depleted back to the ground state when a probe laser excites the molecules to the C 1 Σ + state. A total of 456 rovibrational levels, v = 5–33 and J = 1–11, were observed. A set of Dunham constants and the Rydberg–Klein–Rees (RKR) potential curve for the outer well were reported.

This work presents a simple approach for determining the contribution of Lorentzian or Gaussian statistics by data fitting the spectrum to a Voigt profile. The fitting result shows that the Lorentzian width remains almost constant (∼1.51 MHz) and the Gaussian width increases (∼1.0–2.0 MHz) while changing the laser intensity or atomic density. The frequency shift associated with the cesium 6S–8S two-photon transition as a function of laser power is approximately - 7.25 ( 45 ) Hz / ( mW / mm 2 ), agrees closely with the theoretical value. These results can be used to improve the optical secondary frequency standard in the near infrared region.

The 7 1 Π g Rydberg state of Na 2 correlating with the separated atom limit Na(3s) + Na(5p) has been observed using high-resolution cw optical-optical double resonance spectroscopy. A total of 104 identified rovibrational levels in the range v = 0-12 and 11 ≤ J ≤ 44 have been assigned to the 7 1 Π g state. Dunham coefficients were determined, and the Rydberg-Klein-Rees potential curve in the range of R = 2.99-4.66 A was derived for the 7 1 Π g state using the observed quantum levels. The important molecular properties are the potential minimum T e = 36 633.00(23) cm -1 at R e = 3.6313(29) A, ω e = 115.75(13) cm -1 , and Be = 0.111 22(17) cm -1 . A detailed discussion of this investigation of the 7 1 Π g state is provided.

The 3 1 Δ g and 4 1 Δ g Rydberg states of Na 2 , which dissociate to Na(3s) + Na(4d) and Na(3s) + Na(4f), respectively, have been observed by using high-resolution cw optical–optical double resonance spectroscopy. The potential minima of these two states are separated by 129.74 cm −1 and they have an avoided crossing at 4.09 A implying significant interaction making them a pair of twins. The results of our observation agree very well with the ab initio calculations.

Magnetoelectronic properties of chiral carbon nanotubes and toroids are studied for any magnetic field. They are sensitive to the changes in the magnitude and the direction of the magnetic field, as well as the chirality. The important differences between chiral and achiral carbon nanotubes include band symmetry, band curvature, band crossing, band-edge state, state degeneracy, band spacing, energy gap, and semiconductor–metal transition. Carbon tori also exhibit the strong chirality dependence on the field modulation of discrete states. Chiral carbon tori might differ from chiral carbon nanotubes in energy-gap modulation, density of states, and state degeneracy.

The low-energy electronic properties of multilayer graphite are studied through the tight-binding model. The dependence of electronic properties on the number of layers, the interlayer interactions, and the electric field is investigated in detail. The interlayer interactions destroy the symmetry and the isotropy of energy bands, change linear bands into parabolic bands, and cause the weak overlap of valence and conduction bands. The electric field leads to the subband anticrossing, the change of subband spacing, and the increase of edge states. Dilayer graphite becomes a semiconductor. The effects resulting from interlayer interactions and electric field are completely reflected on the features of density of states, such as two kinds of special structures, the shift of peak position, the change of peak height, and the alternation of band gap.

The splitting of Λ-doubling in the 51Πg Rydberg state of Na2, which dissociates to Na(3s) + Na(4d), has been measured using the high-resolution cw optical–optical double resonance technique. The observed data are in the range of 0 ⩽ v ⩽ 22 and 11 ⩽ J ⩽ 83 with Λ-doubling revealed. A set of Dunham coefficients with Λ-doubling constants has been obtained from the experimental results. The splitting of Λ-doubling increases quadratically with the rotational quantum number J and weakly depends on the vibrational quantum number v. These splitting constants are much larger than those in the Na2 B1Πu state, which dissociates to Na(3s) + Na(3p). This indicates that the splitting of Λ-doubling in the 51Πg state is affected by both the perturbations by adjacent Σ states and the L-uncoupling.

For narrow-gap carbon nanotubes, the curvature effect due to the misorientation of 2 p z orbitals dominates over electronic structures and thus magnetic properties. It significantly changes magnetization and magnetic susceptibility, and creates special structures in them. There exists a critical field direction in changing magnetism. The critical angle strongly depends on the chiral angle, the nanotube radius, and the temperature. One-dimensional carbon nanotubes are quite different from zero-dimensional carbon tori, such as in terms of special structures in magnetization, the strength of the magnetic response, and the critical angle.

The 3 1 Π g state of Na 2 is experimentally investigated by using high resolution cw optical–optical double resonance spectroscopy. A single line Ar + laser (total of 9 lines) is used to pump the sodium dimers from thermally populated ground state X 1 Σ g + to the intermediate B 1 Π u state. Then a single mode Ti:sapphire laser is used to probe the 3 1 Π g state. Violet fluorescence from highly Rydberg excited states (mainly 2 3 Π g or 3 3 Π g states which are transferred from 3 1 Π g state via collisions) to the a 3 Σ u + state is monitored by a filtered photomultiplier tube and a lock-in amplifier. Compared with previous studies [C.C. Tsai, J.T. Bahns, W.C. Stwalley, J. Chem. Phys. 99 (1993) 7417], a wider range of rotational quantum numbers of data field are observed. A set of Dunham coefficients and the Rydberg–Klein–Rees potential energy curve of the 3 1 Π g state are deduced from all the observed rovibrational levels.

The doubly excited valence (3p+3p) 2 1Δg state of Na2 is experimentally observed by using optical-optical double resonance spectroscopy. A single line Ar+ laser (a total of nine lines) was used to pump the sodium dimers from thermally populated ground state X 1Σg+ to the intermediate B 1Πu state. Then, a single mode Ti:sapphire laser was used to probe the doubly excited 2 1Δg state. Violet fluorescence emitted from the highly excited states (mainly 2 3Πg or 3 3Πg states which are transferred from 2 1Δg state via collision) to the a 3Σu+ state was monitored by a filtered photomultiplier tube (PMT). A total of 582 rovibrational levels of 2 1Δg state were observed, identified, and assigned to the vibrational and rotational quantum numbers in the range of 0⩽v⩽28 and 11⩽J⩽99, respectively. The absolute vibrational quantum number assignment was verified by comparing the totally resolved fluorescence with the calculated Franck-Condon factors between 2 1Δg state and B 1Πu state. Dunham coefficients and Rydberg-Kl...

Magnetoelectronic states of carbon toroids have been studied within the tight-binding model. These states are mainly determined by the magnitude and the direction of the magnetic field, and the toroid geometry (chiral angle, height, and radius). The magnetic field can make the angular momentum ( L ) along the longitudinal direction undergo both a large shift and strong coupling. This effect leads to the destruction of state degeneracy, the change of energy spacing, the alternation of quantization of wave function, the vanishing of periodic Aharonov–Bohm oscillations, and the semiconductor–metal transition (SMT). Armchair carbon toroids are quite different from zigzag carbon toroids in features such as state degeneracy, energy gap, existence of the SMT, and dependence on the magnetic field.

Stimulated emission pumping with fluorescence depletion spectroscopy is used to determine the NaD X 1Σ+ ground-state dissociation energy and its isotopic shift. A total of 230 rovibrational levels in the range 9 ≤ v″ ≤ 29 and 1 ≤ J″ ≤ 11 are observed, where v″ = 29 is about 50 cm-1 below the dissociation limit. Analysis of the highest five vibrational levels yields the dissociation energy De = 15 822 ± 5 cm-1 with a vibrational quantum number at dissociation vD = 31.2 ± 0.1. The energy difference in the well depth of this isotopologue with respect to that of NaH is δDe = De(NaH) - De(NaD) = -7 cm-1. A new set of Dunham coefficients is derived to fit all the observed energy levels to within the experimental uncertainty.

For the nf (l=3) series of Na2, quantum defects are calculated from theoretical values of the core quadrupole moment and polarizabilities. They compare favorably with those inferred from our preliminary report of high resolution all-optical triple resonance spectroscopy [Chem. Phys. Lett. 236, 553 (1995)] and from the full report of such spectra given here. The spectrum is the simplest when the higher intermediate state has J′=0 which requires a final state J=1. We predict the stroboscopic effect should first occur when n=52 for the nf series, as we observe, rather than at n=69 for the np series. Our data thus confirm that the strongest series is the nf. Hence the ionization potential is not 39 478.75±0.04 cm−1 as previously reported, but rather 39 478.101±0.013 cm−1, implying a molecular ion dissociation energy of D00(Na2+)=7914.038±0.014 cm−1.

Laser frequency-modulated (FM) spectroscopy has been used as an axial probe of a laser-guided electric discharge in sodium-argon vapor contained in an optically accessible metal heat pipe oven. Absorption measurements in the region 23 106-23 881 cm-1 provided accurate line positions (plusmn;0.006 cm-1) for 141 transitions in the v' = 3-8-- v" = 0 and v' = 5-9-- v" = 1 bands of NaH (A1Sigma+-X1Sigma+). In addition, 18 transitions of Na (3p to 9-13d and 11-14s) and 10 of argon (5p-4s) were measured. Analysis of the spectrum indicates that perhaps all absorption signals are due to neutrals NaH, Na, and Ar and are observed via "population" modulation. Copyright 1997 Academic Press. Copyright 1997Academic Press

We determine the energies of twelve vibrational levels lying within 20 GHz of the lowest dissociation limit of ${}^{85}{\mathrm{Rb}}_{2}$ with two-color photoassociation spectroscopy of ultracold ${}^{85}\mathrm{Rb}$ atoms. The levels lie in an energy range for which singlet and triplet states are mixed by the hyperfine interaction. We carry out a coupled channels bound state analysis of the level energies, and derive accurate values for ${}^{85}{\mathrm{Rb}}_{2}$ interaction parameters. The information obtained is sufficient to allow for quantitative calculations of arbitrary Rb ultracold collision properties.

The observation of Bose-Einstein condensation ~BEC! in dilute ultracold gas samples of rubidium @1#, lithium @2#, and sodium atoms @3# has made it possible to study this macroscopic quantum phenomenon in its pure form without complicated modifications due to strong interactions. A variety of experiments has been proposed or already carried out, fascinating examples being the observation of collective shape oscillations and the observation of the relative phase of two Bose-Einstein condensates @4,5#. A rich variety of other experiments would come into reach if one could alter arbitrarily, possibly even in real time, the sign and magnitude of the atom-atom scattering length a. The scattering length occurs as the coefficient of the condensate self-interaction term in the condensate wave equation and has a profound effect on the stability and other properties of the condensate. An opportunity to change this parameter would arise if it were possible to tune the scattering length by means of external fields, i.e., either a static magnetic field @6# or a timedependent optical @7# or rf field @8#.

We observe a shape resonance in the scattering of two ultracold $^{87}\mathrm{Rb}$ atoms, causing the colliding atoms to form a long-living compound system inside an l=2 centrifugal barrier. Its existence follows from a photoassociation experiment in a gas sample of doubly polarized $^{87}\mathrm{Rb}$ atoms. Using it we are able to carry out direct determinations of the triplet scattering length for $^{87}\mathrm{Rb}$, relevant to Bose-Einstein condensation experiments, and of the Rb+Rb ${\mathrm{C}}_{6}$ dispersion coefficient. Consequences for the $^{85}\mathrm{Rb}$ scattering length are discussed.

Photoassociation resonances in the ${}^{87}$Rb${}_{2}$ ${1}_{g}$ state dissociating to $5{\phantom{\rule{0.16em}{0ex}}}^{2}S+5{}^{2}{P}_{1/2}$ were produced by the excitation of colliding ${}^{87}$Rb atoms in a far-off resonance trap. Levels down to 31 cm${}^{\ensuremath{-}1}$ below the dissociation limit were measured with resonance linewidths of 15 to 20 MHz, and have been located to a one-sigma combined systematic and statistical uncertainty of 50 MHz relative to the $5{\phantom{\rule{0.16em}{0ex}}}^{2}S+5{}^{2}{P}_{1/2}$ limit. Electron and nuclear spins were fixed to a space-fixed axis by circularly polarized optical pumping, so that only states with total nuclear spin $I=3$ were excited, thereby greatly simplifying the spectrum. The analysis of the data yielded hyperfine coupling parameters $A(v)$, vibrational $G(v)$, and rotational $B(v)$ parameters. The $G(v)$ parameters could be fit to an rms accuracy of about 0.01 cm${}^{\ensuremath{-}1}$ to a potential constructed from current ${C}_{3}$ and ${C}_{6}$ long-range dispersion parameters plus an ab initio potential that was adjusted in depth and with quadratic terms in the internuclear distance added to the inner wall.

In our previous research, Cordyceps militaris (CM) had a hypoglycemic effect in normal rats. In this study we wanted to elucidate whether CM also had an effect on diabetic rats. Twelve rats with streptozotocin-induced diabetes were separated randomly into 2 groups. First, aqueous extracts of CM 10 mg/kg (CM group) or saline (control group) was fed to the rats; then the plasma glucose levels were assayed. Second, the signaling proteins IRS-1 and GLUT-4 collected from the muscle were detected. Finally, another 2 groups of rats were injected with atropine 0.1 mg/kg intraperitoneally just before the CM/saline feeding, and the assays mentioned above were repeated. Blood glucose decreased 7.2% in the CM group but only 1.5% in the control group (P < 0.05). The IRS-1 signal was 2.9-fold higher than actin in the CM group but only 0.8-fold higher in the control group (P < 0.005). In GLUT-4 signal, the difference was 1.7- vs. 0.6-fold, respectively, compared with actin (P < 0.05). However, atropine injection made CM-induced hypoglycemia or elevation of IRS-1 and GLUT-4 not significant. In conclusion, CM had a hypoglycemic effect in diabetic rats and atropine blocked it. Therefore, the cholinergic activation also was considered to be involved in the hypoglycemic effect of CM in rats with streptozotocin-induced diabetes.

This paper thoroughly elucidates the relative intensities of the probe transmission in a ladder-type electromagnetically induced transparency (EIT) system by considering the optical pumping effect. The observed EIT spectra reveal a different probe or coupling power dependence for various transmission peaks. In addition to causing quantum interference, the probe and coupling laser fields realign the population of Zeeman sublevels in the ground state through optical pumping. Analytical results indicate that the re-distribution levels, failing to contribute to the EIT peaks, either out of transition path or zero transition probability, significantly affect the transmission intensity.

Using a homemade ultrasensitive space charge limited ion detector, the K 2 singlet gerade states (7–9 1 Σ + g and 4 1 Π g ) were observed for the first time. The exotic potential of the double minimum 7 1 Σ + g state was constructed using a hybrid approximation method. The molecular constants and the Rydberg–Klein–Rees (RKR) potential curve for the 9 1 Σ + g state were obtained. The 8 1 Σ + g and 4 1 Π g states were partially characterized.

Recent developments in laser cooling and evaporative cooling techniques, especially for alkali gas samples, have led to the rapidly expanding field of cold collision physics. Collisions between cold atoms are exceptional in a number of aspects. One of these is the frequent occurrence of shape resonances, which are elastic scattering resonances associated with quasibound diatomic levels trapped behind a centrifugal barrier. These are important to the collision physics because the collision energies are typically lower than the centrifugal barrier even for the lowest nonvanishing l partial waves. Considering the vibrational and rotational energy spacings of the alkali dimers, the probability for any of these to have at least one quasibound state with l # 6 is more than 50%. Knowing the energy of a shape resonance leads very directly to an accurate scattering length for the corresponding potential and is nearly equivalent to finding the last bound state of that potential. Shape resonances may be expected to create possibilities for many exciting new experiments. In particular, they will shed new light on the elastic and inelastic interactions of cold atoms, which are of crucial importance for understanding Bose-Einstein condensation phenomena [1 ‐ 3], laser-cooled atomic clocks [4], and other cold-atom applications. They may also lead to a new kind of spectroscopy of states inside the centrifugal barrier with a tunneling lifetime long enough for inelastic interactions to occur due to weak interaction terms that are difficult to study otherwise. In this Letter, we present the first detailed study of a shape resonance in cold atomic scattering, focusing our attention on a g-wave resonance in the scattering of two 85 Rb atoms. We observe this resonance with cold-atom photoassociation [5‐10]. Photoassociation is particularly useful for the present study, since it allows us to excite atomic pairs in a narrow radial range around 40a0 that is inside the centrifugal barrier at about 100a0, and also because it allows us to probe individual partial wave components of the collision [10]. That is, we can selectively photoexcite the collision resonance. The 85 Rb 1 85 Rb g-wave shape resonance is sufficiently long lived that we are also able, for the first time, to directly observe time dependence in cold atomic collisions. With a pulsed photoassociation experiment, we measure the buildup of the resonance state by tunneling through the barrier in competition with various decay processes. The lifetime of the shape resonance is also long enough to be comparable to the time scale for inelastic interaction processes in the scattering of Rb ground state atoms. In agreement with this the time-independent photoassociation spectrum associated with the excitation of a J › 4 excited rotational state shows anomalous features that cannot be reproduced in terms of elastic scattering alone. The anomalous features can be explained in terms of an additional broadening of the resonance due to inelastic decay channels.

The 1 3Δg state of Na2 has been studied extensively by both filtered fluorescence and ionization detection and analyzed by both Dunham‐type expansion and near‐dissociation expansion (NDE) models in the analysis. Our observations have covered 99.998% of the potential well depth with the outermost Rydberg–Klein–Rees (RKR) turning point at 28.02 A. NDE analysis gives Te=28 032.468 (±0.021) cm−1, De=7162.436 (±0.021) cm−1, and Re=3.463 81 (±0.000 28) A. Significant long‐range behavior in the near dissociation levels has been observed. Fitting of the RKR turning points gives the long‐range coefficients C5=1.388 (±0.031)×106 cm−1 A5 and C6=0.4008 (±0.0046)×108 cm−1 A6. These newly observed results show reasonable agreement with recent theoretical calculations.

Five bound nd 1 Δ g ( n = 11-15) electronic states have been investigated using optical-optical double resonance excitation followed by ionization detection using an ultrasensitive space charge limited diode, which detects ion signals (presumably K + 3 produced by associative ionization). The molecular constants and the Rydberg-Klein-Rees potential curves for these states have been generated. The dissociation energies, additional binding energies, and molecular constants due to the weakly bound Rydberg bonding δ g orbitals are discussed.

The 4 3Σ+g, 3 3Πg, and 2 3Δg states of K2 have been studied by perturbation facilitated optical–optical double resonance spectroscopy for the first time. Molecular constants of those states are derived and compared with theoretical calculations. Varying the trial vibrational quantum numbers of these upper states, absolute vibrational quantum number assignments are obtained by comparison between the observed resolved fluorescence intensities and the calculated Franck–Condon factors. The Rydberg–Klein–Rees potential curves are constructed and compared with theoretical calculations. Finally, the observation of the lowest ‘‘dark’’ vibrational levels of the b 3Πu state by resolved fluorescence from the 2 3Δg state confirmed the absolute vibrational numbering of this state and allowed refinement of the b 3Πu molecular constants.

A modified internuclear distance criterion, R LR- m , as the lower bound for the region of validity of the inverse-power expansion of the diatomic long-range potential is proposed. This new criterion takes into account the spatial orientation of the atomic orbitals while retaining the simplicity of the traditional Le Roy radius, R LR for the interaction of S state atoms. Recent experimental and theoretical results for various excited states in Na 2 suggest that this proposed R LR- m is an appropriate generalization of R LR .