Lambda Doubling Research Articles

The millimeter-wave spectrum of the SiP radical (X2Πi): Rotational perturbations and hyperfine structure.

The millimeter/submillimeter-wave spectrum of the SiP radical (X2Πi) has been recorded using direct absorption spectroscopy in the frequency range of 151-532GHz. SiP was synthesized in an AC discharge from the reaction of SiH4 and gas-phase phosphorus, in argon carrier gas. Both spin-orbit ladders were observed. Fifteen rotational transitions were measured originating in the Ω = 3/2 ladder, and twelve in the Ω = 1/2 substate, each exhibiting lambda doubling and, at lower frequencies, hyperfine interactions from the phosphorus nuclear spin of I = 1/2. The lambda-doublets in the Ω = 1/2 levels appeared to be perturbed at higher J, with the f component deviating from the predicted pattern, likely due to interactions with the nearby excited A2Σ+ electronic state, where ΔEΠ-Σ ∼ 430cm-1. The data were analyzed using a Hund's case aβ Hamiltonian and rotational, spin-orbit, lambda-doubling, and hyperfine parameters were determined. A 2Π/2Σ deperturbation analysis was also performed, considering spin-orbit, spin-electronic, and L-uncoupling interactions. Although SiP is clearly not a hydride, the deperturbed parameters derived suggest that the pure precession hypothesis may be useful in assessing the 2Π/2Σ interaction. Interpretation of the Fermi contact term, bF, the spin-dipolar constant, c, and the nuclear spin-orbital parameter, a, indicates that the orbital of the unpaired electron is chiefly pπ in character. The bond length in the v = 0 level was found to be r0 = 2.076 Å, suggestive of a double bond between the silicon and phosphorus atoms.

Laboratory and Astronomical Detection of the SiP Radical (X2Π i ): More Circumstellar Phosphorus

The millimeter-wave spectrum of the SiP radical (X2Πi) has been measured in the laboratory for the first time using direct-absorption methods. SiP was created by the reaction of phosphorus vapor and SiH4 in argon in an AC discharge. Fifteen rotational transitions (J + 1 ← J) were measured for SiP in the Ω = 3/2 ladder in the frequency range 151–533 GHz, and rotational, lambda doubling, and phosphorus hyperfine constants determined. Based on the laboratory measurements, SiP was detected in the circumstellar shell of IRC+10216, using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory at 1 mm and 2 mm, respectively. Eight transitions of SiP were searched: four were completely obscured by stronger features, two were uncontaminated (J = 13.5 → 12.5 and 16.5 → 15.5), and two were partially blended with other lines (J = 8.5 → 7.5 and 17.5 → 16.5). The SiP line profiles were broader than expected for IRC+10216, consistent with the hyperfine splitting. From non-LTE radiative transfer modeling, SiP was found to have a shell distribution with a radius ∼300 R *, and an abundance, relative to H2, of f ∼ 2 × 10−9. From additional modeling, abundances of 7 × 10−9 and 9 × 10−10 were determined for CP and PN, respectively, both located in shells at 550–650 R *. SiP may be formed from grain destruction, which liberates both phosphorus and silicon into the gas phase, and then is channeled into other P-bearing molecules such as PN and CP.

Calculation of Lambda Doubling for 7LiH1 molecule Using the System band emission for electronic transmissions

The A2?u-X1?g+ emission band system of 7LiH1 molecule has been calculated for Lambda doubling. The relation between wave number ?p , ?Q , ?R conducted the energies of the state of rotation F (J), and (J + 1) with rotational quantum number J, respectively, of 7LiH1 molecule for statehood A2?u using the rotation, fixed vibrational states of both the ground and raised crossovers vibrational against ???= 0 to V ' = 0-4using rotational levels J = 0 to J = 20 have found.

Calculation of Lambda Doubling for 7LiH1 molecule Using the System band emission for electronic transmissions

The A2?u-X1?g+ emission band system of 7LiH1 molecule has been calculated for Lambda doubling. The relation between wave number ?p , ?Q , ?R conducted the energies of the state of rotation F (J), and (J + 1) with rotational quantum number J, respectively, of 7LiH1 molecule for statehood A2?u using the rotation, fixed vibrational states of both the ground and raised crossovers vibrational against ???= 0 to V ' = 0-4using rotational levels J = 0 to J = 20 have found.

Resonant two-photon ionization spectroscopy of jet-cooled tantalum carbide, TaC

The optical spectrum of diatomic TaC has been investigated for the first time, with transitions recorded in the range from 17,850 to 20,000 cm(-1). Six bands were rotationally resolved and analyzed to obtain ground and excited state parameters, including band origins, upper and lower state rotational constants and bond lengths, Fermi contact parameter b(F) for the ground state, and lambda doubling parameters for the excited states. The ground state of TaC was found to be X (2)Sigma(+), originating from the 1sigma(2)2sigma(2)1pi(4)3sigma(1) electronic configuration, in which only the valence orbitals arising from the Ta(5d+6s) and C(2s+2p) orbitals are listed. All of the rotationally resolved and analyzed bands were found to originate from the ground state, giving B(0)"=0.489 683(83) cm(-1), r(0)"=1.749 01(15) A, and b(F)"=0.131 20(36) cm(-1) (1sigma error limits) for (181)Ta (12)C. Comparison of the Fermi contact parameter to the atomic value shows that the 3sigma orbital is approximately 75% Ta 6s in character. The other group 5 transition metal carbides, VC and NbC, have long been known to have 1sigma(2)2sigma(2)1pi(4)1delta(1), (2)Delta ground states, with low-lying 1sigma(2)2sigma(2)1pi(4)3sigma(1), (2)Sigma(+) excited states. The emergence of a different ground state in TaC, as compared to VC and NbC, is due to the relativistic stabilization of the 6s orbital in Ta. This lowers the energy of the 6s-like 3sigma orbital in TaC, causing the 1sigma(2)2sigma(2)1pi(4)3sigma(1), (2)Sigma(+) state to fall below the 1sigma(2)2sigma(2)1pi(4)1delta(1), (2)Delta state.

The rotational spectrum of CoF in all three spin-orbit components of the XΦi3 state

The pure rotational spectrum of cobalt monofluoride in its X (3)Phi(i) electronic state has been measured in the frequency range of 256-651 GHz using direct absorption techniques. CoF was created by reacting cobalt vapor with F(2) in helium at low pressure (25-30 mTorr). All three spin components were identified in the spectrum of this species, two of which exhibited lambda doubling. Each spin component showed hyperfine splittings from both nuclei: an octet pattern arising from the (59)Co spin of I=72, which is further split into doublets due to the (19)F nucleus (I=12). The data were fitted close to experimental precision using an effective Hamiltonian expressed in Hund's case (a) form, and rotational, fine structure, hyperfine, and lambda-doubling parameters were determined. There is evidence that the rotational levels of the highest spin component (3)Phi(2) are perturbed. The r(0) bond length of CoF was estimated from the rotational constant to be 1.738 014(1) A. This value is in good agreement with previous studies but much more accurate. The matrix elements necessary for the complete treatment of Lambda doubling in a Phi state have been derived and are presented for the first time.

Low temperature capture of open shell dipolar molecules by ions: the capture of rotationally selected NO(2Π1/2, j) by C+

The low-energy capture of dipolar diatomic molecules in an open electronic state by ions is usually considered to be induced by the first-order charge-permanent dipole interaction with other terms of the long-range potential playing a minor role. If the molecular dipole moment is anomalously small (as is the case for slightly asymmetrical molecules), however, the situation changes, and the capture dynamics is strongly affected by higher orders of the charge-permanent dipole, charge-permanent quadrupole, and charge-induced dipole interactions. The interplay of different terms in the interaction potential manifests itself in complicated temperature dependence of the rotationally state-specific capture rate coefficients. These features of the capture are studied by way of example for NO(X (2)Pi(1/2), j) + C(+) collisions in the temperature range 10(-2)-20 K where the dynamics is adiabatic with respect to rotational and fine-structure transitions and sudden with respect to transitions between Lambda doubling and hyperfine states. The theoretical rate coefficient, which depends on the translational and rotational temperature, agrees with the experimental one measured at T(tr) = 0.6 K and T(rot) = 20 K.

A molecular-beam optical Stark study of lines in the (1,0) band of the FΔ7∕24-XΔ7∕24 transition of iron monohydride, FeH

A supersonic molecular beam of iron monohydride, FeH, has been generated using a laser ablation/chemical reaction scheme and probed at near-natural linewidth resolution by optical Stark spectroscopy utilizing laser-induced fluorescence detection. The observed Stark splitting in Q(3.5) and R(3.5) lines of the F4delta(7/2) <-- X4delta(7/2) (1,0) transition were analyzed to determine values for the magnitudes of the permanent electric dipole moments, absolute value(mu), which were found to be 2.63(3) and 1.29(3) D for the X4delta (v = 0) and F4delta (v = 1) states, respectively. A comparison with ab initio theoretical predictions is made. The lambda doubling in the low-J levels of the F4delta(7/2) (v = 1) state is also modeled.

Observation of L uncoupling in the 5Δg1 Rydberg state of Na2

The phenomenon of electronic orbital angular momentum L uncoupled from its internuclear axis has been observed in the sodium dimer using high-resolution cw optical-optical double-resonance spectroscopy. When L uncoupling occurs, the degeneracy of Lambda doubling is removed. In our experiment, the intermediate B (1)Pi(u) state of Na(2) is excited from the thermally populated ground X (1)Sigma(g) (+) state by a single-line Ar(+) laser. Then, a single-mode dye laser is used to probe the Rydberg states from the intermediate state. The signals are detected by monitoring the UV fluorescence from the triplet gerade states back to the a (3)Sigma(u) (+) state via collision energy transfer. Under our experimental resolution, the splitting of Lambda doubling in the 5 (1)Delta(g) state of Na(2) can be measured. A total of 136 rovibronic levels with ef parities have been assigned to the 5 (1)Delta(g) state. The Lambda-splitting constants deduced from these data are q(0)=0.376(90)x10(-4) cm(-1), q(v)=0.114(6)x10(-4) cm(-1), and mu=0.76(33)x10(-8) cm(-1). In general, the Lambda splitting of the Delta states is considerably smaller than that of the Pi states. However, the first-order splitting constants q(0) and q(v) reported here are larger than those in the B (1)Pi(u) state. This is due to the L uncoupling of the Rydberg states.

High-resolution spectroscopy of CoS (XΔi4): Examining 3d transition-metal sulfide bonds

The pure rotational spectrum of CoS, the cobalt sulfide radical, has been measured using direct absorption techniques in the frequency range of 180-540 GHz. This study is the first spectroscopic investigation of any kind of this molecule. CoS was created by reacting cobalt vapor with H2S. Four spin components were identified in the spectra of this species, one of which exhibited lambda doubling, identifying the ground state as 4Deltai. Transitions arising from the lowest spin component of the less abundant Co 35S isotopomer have also been detected, as well as from v=1 and v=2 of the main species. The spectra were readily identified because each spin component exhibited an octet pattern arising from the 59Co spin of I=72. The data were fit using Hund's case (a) Hamiltonian, and rotational, fine-structure, hyperfine, and lambda-doubling constants were determined. The hyperfine parameters support a delta3pi2 electron configuration and are consistent with some orbital overlap between the metal and sulfur atoms. From the rotational constant, the bond length of CoS was calculated to be r0=1.977 985 06(10) A. This bond length is significantly shorter than that of MnS or FeS, in contrast to the bond distances found in the oxide analogs which are all similar in value. These results indicate that the 3d metal sulfides differ somewhat from their oxide counterparts, probably due to the availability of sulfur p orbitals for bonding.

The visible spectrum of rhodium monoxide: Rh 16O and Rh 18O

Spectroscopic observations are reported for rhodium monoxide from hollow-cathode emission and laser-induced fluorescence experiments. Eleven bands of Rh 16O and 10 of Rh 18O, from the [15.8] 2Π– X 4Σ − (b) and [16.0] 2Π– X 4Σ − (b) transitions, have been rotationally analyzed. The ground state constants have been determined as B 0 = 0.4132, λ 0 = −0.58 and γ 0 = −0.102, in cm −1. Rotational and lambda doubling parameters in v = 0, 1, 2, and 3 excited state vibrational levels have also been determined.

Electronic spectra of iron monohydride in the infrared near 1.35 and 1.58 microm.

The complex, many-line spectrum of FeH, lying in the infrared region between 5500 and 7500 cm(-1), has been shown to consist of two separate electronic transitions: E (4)Pi-X (4)Delta and E (4)Pi-A (4)Pi. High resolution Fourier transform spectra from thermal emission have been rotationally analyzed in detail. Lambda doubling in both the E (4)Pi and A (4)Pi states is considerable. The experimentally determined energies and bond lengths of the newly characterized states are in good agreement with theoretical predictions.

Methods for constraining fine structure constant evolution with OH microwave transitions.

We investigate the constraints that OH microwave transitions in megamasers and molecular absorbers at cosmological distances may place on the evolution of the fine structure constant alpha=e(2)/ variant Planck's over 2pi c. The centimeter OH transitions are a combination of hyperfine splitting and lambda doubling that can constrain the cosmic evolution of alpha from a single species, avoiding systematic errors in alpha measurements from multiple species which may have relative velocity offsets. The most promising method compares the 18 and 6 cm OH lines, includes a calibration of systematic errors, and offers multiple determinations of alpha in a single object. Comparisons of OH lines to the HI 21 cm line and CO rotational transitions also show promise.

Rotational Rest Frequencies for CrO (X5Πr) and CrN (X4Σ−)

The pure rotational spectra of CrO (X 5Πr) and CrN (X 4Σ-) have been recorded using millimeter/submillimeter-wave spectroscopy in the frequency range 248-636 GHz. These radicals were created by the reaction of chromium vapor, produced in a Broida-type oven, with N2O or NH3 under DC discharge conditions. For CrO, 12 rotational transitions were recorded, in which up to five spin-orbit components were observed—the first measurement of the pure rotational spectrum of a molecule in a 5Π electronic state. Nine rotational transitions were recorded for CrN; here all four spin components were measured in every transition. The data obtained for both radicals were analyzed using an appropriate effective Hamiltonian. The resulting spectroscopic parameters of these species were determined to high precision, including those related to fine structure and lambda doubling. This work will enable radioastronomical searches for CrN and CrO to be carried out. CrO has already been observed in the optical spectra of stellar atmospheres.

Contributions of diatomic molecular electronic systems to heated air radiation

A spectroscopic database has been constructed for all the contributing electronic systems of air diatomic molecules for elevated temperatures (up to 15,000 K ). The electronic systems which have been investigated are N 2 first- and second-positive, Birge–Hopfield 1 and 2, Carroll–Yoshino, Worley and Worley–Jenkins, N 2 + Meinel, first- and second-negative, O 2 Schumann–Runge and NO γ,β,δ,ε,γ′,β′,11,000 A ̊ and infrared. The RKR potentials have been reconstructed in order to calculate the vibrational wavefunctions, and the electronic-vibrational part of line intensities has been computed with up-to-date ab-initio electronic transition moment functions. The results of our calculated vibrational band strengths are in good agreement with the available measurements. The positions and intensities of the rotational lines have been determined in intermediate a/b Hund's coupling case with up-to-date molecular constants, and the lambda doubling has been resolved when related parameters were available in the literature. Absorption spectra and the optically thin radiation source strengths of the studied electronic systems are presented and discussed in terms of their comparative contribution to emission and absorption.

High resolution spectroscopy and spectral simulation of C2 using degenerate four-wave mixing

Degenerate four-wave mixing in the sub-Doppler phase conjugate geometry was used to record high resolution spectra of the d 3Πg–a 3Πu (0–0) Swan band of C2 produced in an oxy-acetylene flame. The line positions of isolated transitions were measured to an accuracy of ∼3×10−3 cm−1 and calibrated using a Fizeau interferometer system. The data obtained from these spectra was used to calculate rotational constants and lambda doubling parameters for the 3Π states from which the line positions for the whole band were calculated. Noticeable improvements between experimental and calculated line positions are seen when compared to previously published values. The effect of inaccuracies in line positions on the simulation of degenerate four-wave mixing spectra is discussed and some examples of the improvement in simulation using the newly calculated line positions are presented.

Studies of rotational level Λ-doubling by rf-optical double resonance spectroscopy: application to NaK D1Π

We report here the application of optical-radio frequency double resonance spectroscopy for individual rotational levels of the NaK D 1 Π state. Lambda doubling constant q values for five ν′, J′ levels are obtained. These data are combined with measurements of dc e- f Stark-mixing-induced changes in optical spectra, and the electric dipole moment d p in the D 1 Π state is determined.

Laboratory Detection of the C[TINF]9[/TINF]H Radical

The linear carbon chain radical C9H in its 2Π1/2 electronic ground state has been detected in a Fourier transform microwave spectrometer with a supersonic pulsed-jet discharge nozzle. The frequencies of 44 rotational transitions between 5.4 and 16.1 GHz have been measured to a few parts in 107, from which precise values for the rotational, centrifugal distortion, lambda doubling, and hyperfine constants have been determined. These allow calculation of the entire radio spectrum of the ground state of C9H to a fraction of 1 km s-1 in equivalent radial velocity.

Laser Spectroscopy of the Lanthanide Monofluorides: Analysis of theA2Π–X2Σ+Transition of Ytterbium Monofluoride

High-resolution excitation spectra have been obtained of several bands in theA2Π–X2Σ+transition of172YbF,174YbF, and176YbF. Vibrational, rotational, and spin–rotation constants have been determined for the groundX2Σ+state of the three isotopomers. The vibrational frequency, ωe= 506.6681(91) cm−1, of174YbF, the most abundant isotopomer, confirms the assignment of this state to the Yb+(4f146s)F−configuration. Vibrational spacings and rotational, spin–orbit, and lambda doubling constants have been calculated for theA2Π state, which is heavily perturbed. Two vibrational levels of a new Ω = 0.5 state have been observed in the vicinity of theA2Π1/2state and analysis of the rotational structure and lambda (or omega) doubling of these levels indicates that this is the perturbing state. Analysis of the isotope structure establishes the vibrational numbering of the two levels asv= 0 and 1. The deperturbed vibrational spacing in this state is calculated to be ∼605 cm−1and suggests that the state originates in the Yb+(4f136s2)F−configuration. The lambda doubling in theA2Π1/2state, originating in the Yb+(4f146p) configuration, is examined in terms of its interaction with theB2Σ+state, which comes from the same configuration. Discrepancies between observed and calculated values, especially forA2Π1/2v= 1, provide further evidence for the perturbation.

Lifetime measurements of He2- by means of a heavy-ion storage ring

The lifetime of the metastable autodetaching 4Pig state of the He2- ion has been measured by a time-of-flight technique to be 135+or-15 mu s, using a heavy-ion storage ring. The lifetime is nearly a factor of three shorter than the only available theoretical prediction. It is proposed that the lifetime should be assigned to the 4Pig- Lambda doubling component.