Microwave-optical Double Resonance Spectroscopy Research Articles

Fault-tolerant Hahn-Ramsey interferometry with pulse sequences of alternating detuning

A scheme for efficient correction of driving-field frequency drifts in Ramsey interferometry is proposed. The two off-resonant $\ensuremath{\pi}/2$ pulses of duration $T$ used in the traditional Ramsey setup are supplemented with an additional pulse of duration $2T$ (approximate $\ensuremath{\pi}$ pulse), which is applied midway between the Ramsey pulses and has a detuning of opposite sign to theirs. This scheme, which resembles a Hahn's spin-echo pulse embedded into the Ramsey setup, corrects small-to-moderate random errors in the detuning of the driving field. This allows the observation of Ramsey fringes of high contrast even with a noisy driving field or in inhomogeneously broadened atomic ensembles. The contrast is further improved by replacing the refocusing $2T$ pulse by a composite $\ensuremath{\pi}$ pulse. We demonstrate the validity of the concept by comparing experimental results from usual Ramsey measurements with Hahn-Ramsey measurements. These experimental results are obtained from microwave-optical double-resonance spectroscopy on $^{171}\mathrm{Yb}{}^{+}$ ions in a segmented linear Paul trap. In the same way, we verify qualitatively the predicted advantage from using a composite $\ensuremath{\pi}$ pulse for refocusing.

Microwave optical double resonance spectroscopy of ammonia in a hollow-core fiber

We have demonstrated microwave optical double resonance spectroscopy of the nu(1) + nu(3) and nu(1) + 2nu(4) bands of ammonia in a hollow-core photonic bandgap fiber. Signal strength and lineshapes are analyzed. Spectroscopic assignments of previously assigned lines and previously proposed assignments have been confirmed and new assignments have been made. Several microwave transitions in the excited vibrational states have been measured for the first time.

Ionic crystals in a linear Paul trap.

We describe a configuration for a linear Paul rf ion trap. This trap can store a long string of ions with a small second-order Doppler shift, comparable to that achieved with a single ion in a quadrupole Paul trap. Crystallized strings of trapped ions, as well as more complicated structures, have been observed in the trap. We report an observation of the 40.5-GHz ground-state hyperfine interval of $^{199}\mathrm{Hg}^{+}$ by microwave-optical double-resonance spectroscopy and discuss prospects for a microwave frequency standard based on a trapped string of ions.

Linear Trap for High-accuracy Spectroscopy of Stored Ions

Abstract In a linear r.f. Paul trap, ‘crystallized’ structures of laser-cooled 199Hg+ ions are observed. The ground-state hyperfine transition at 40·5 GHz is observed in microwave-optical double-resonance spectroscopy. Future prospects are also discussed.

Comment on “Predissociation of ammonia à state studied by microwave—optical double resonance spectroscopy”

The rotational dependence of the predissociation rate for NH 3 (Ã) v = 0 observed by Endo, Iida and Ohshima is shown to be fully compatible with earlier calculations based on the centrifugal modification of the effective barrier to dissociation.

Predissociation of ammonia à state studied by microwave—optical double-resonance spectroscopy

Homogeneous linewidths of the individual rotational transitions in the ÃX̃ system of ammonia were determined precisely by a microwave—optical double-resonance technique, where a single inversion transition in the ground state was selected by microwave radiation, and subsequent electronic transitions were observed by changes in the microwave absorption. The linewidths, which directly correspond to the à state predissociation rates, increase with J but are nearly independent of K. Small but distinct asymmetry in the line shape was observed for the first time.

The permanent electric dipole moment of CaOH

Theoretical calculations yield electric dipole moments ( μ) of 0.98, 0.49, and 0.11 Debye at the computed equilibrium geometries of the X 2Σ+, A 2Π, and B 2Σ+ states of CaOH. Thus the pure rotational spectra in these electronic states are expected to be weaker than the corresponding alkaline monohalides. This is consistent with our failure to observe the pure rotational spectrum of the X 2Σ+ state by microwave-optical double resonance spectroscopy, and is in agreement with our experimental determination of μ<1 D for the A 2Π3/2 state. However, the vibrational–rotational spectrum is quite strong, since dμ/dr is quite large in these ionic molecules. Using the free-ion polarizabilities, the modified Rittner model predicts a μ value of about −8 D for the X 2Σ+ state, which is in error by about 9 D. The theoretical values for total dipole moment, as well as contributions from Ca+ and OH−, can be reproduced using effective polarizabilities. However, this analysis shows that the effective polarizability of OH− is a much smaller fraction of the free-ion value than for Ca+, because Pauli repulsion restricts the OH− polarization toward the Ca+. Some account of this effect seems to be a prerequisite for the successful application of either Rittner or ligand field models to ionic systems.

Hyperfine coupling constants of the CCN radical in the à 2Δ(000) state by microwave–optical double resonance spectroscopy

Electric-dipole allowed transitions between hyperfine components and between rotational levels have been observed for CCN in the à 2Δ(000) state by a technique of microwave–optical double resonance. The observed transition frequencies have been analyzed to yield 14N hyperfine coupling constants: a=50.22(19), b=−5.9(12), c=7.8(20), and eQq=0.75(54), all in MHz with one standard error in parentheses. An attempt was made to observe Λ-doubling transitions and rotational transitions in the X̂ 2Π(000) state without success.

Dipole moments of H 2CS in the [formula omitted] and [formula omitted] states by MODR spectroscopy

The microwave-optical double resonance (MODR) technique was used to measure the Stark effects of H 2CS in the A ̃ 1A 2 (v = 0) and a ̃ 3A 2 (v 3 = 1) states, from which the dipole moment has been calculated to be 0.850(2)D and 0.548(9)D for the two states, respectively, where the numbers in parentheses denote one standard error and apply to the last digits. The Stark effect measurement using MODR was compared with that from Doppler-limited laser excited fluorescence.

Laser spectroscopy and microwave-optical double resonance of a supersonic expansion ICl A 3п (1) υ = 19

The 19-0 band of the I35Cl A 3п(1)-X 1Σ+ system is examined at sub-Doppler resolution using a single mode dye laser and a supersonic jet. Complex hyperfine structure is resolved and assigned with the aid of microwave-optical double resonance spectroscopy. Twenty-two microwave transitions were observed within the excited vibronic state and the subsequent analysis results in values for the rotational constant, Ω-doubling constant, two electric quadrupole constants and a magnetic hyperfine constant.

Microwave optical double resonance spectroscopy of ND2 in (000) of X̃ 2B1

Microwave optical double resonance spectroscopy has been used to observe in excess of 200 microwave transitions involving 21 rotational levels in the (000), X̃ 2B1 state of ND2. The observed transitions have been fitted to two model Hamiltonians. In the first fit, accurate values for the spin rotation constants and 2D hyperfine constants were determined. The 2D hyperfine constants are in excellent agreement with those calculated from 1H parameters in NH2, (000) X̃ 2B1. In the second fit, only the constants of the Hamiltonian describing the spin-rotation effect were determined. The derived spin-rotation parameters for ND2 (As, Bs, Cs, ΔsK, ΔsN, ΔsNK + ΔsKN, δsK, and δsN) are compared to the appropriate scaled constants of NH2.

Microwave optical double resonance used as an assignment tool in optical spectroscopy

Microwave transitions between excited rovibronic states were used to assign transitions in the optical spectrum of NH 2 using microwave optical double-resonance spectroscopy. The microwave frequency was set so as to pump one particular hyperfine component of the previously observed 1 10, J = 1 2 , Π(0, 10, 0), A ̃ 2A 1 ↔ u , F 2 transition around 6.3 GHz, the frequency of the dye laser was then tuned over a wide spectral range. Double-resonance signals occurred in four level systems whenever the optically excited level was collisionally coupled to either of the microwave pumped levels. This method, when used in conjunction with the results of a conventional absorption spectrum of the molecule, yields information on perturbing states around the Π(0, 10, 0) region. In addition it has proved possible to detect further levels of similar vibronic character to the u state, in particular the spin rotation partners of u and u′. Some discussion on a possible vibronic assignment for these levels is included.

Microwave optical double resonance spectrum of NH2. VII. Hyperfine coupling constants (14N and 1H) in Σ(0, 9, 0) and Π (0, 10, 0) of a Ã2A1

Magnetic dipole allowed transitions NKaKc J = N−1/2 ↔ J = N+1/2 have been observed in two vibrational states Σ(0,9,0) and Π (0,10,0) of ? 2A1 NH2 using microwave optical double resonance spectroscopy. Extensive hyperfine structure involving both ortho and para rotational states has been analyzed to yield 14N and 1H magnetic hyperfine coupling constants for the Π (0,10,0) vibronic state; the Σ (0,9,0) data were not sufficient alone to determine all these constants. The hyperfine structure of Σ (0,9,0) and Π (0,10,0) could not be fitted simultaneously with a single set of hyperfine coupling constants. However, contrary to our expectations and some previous analyses, no significant difference between the Fermi contact terms for 14N in the Σ (0,9,0) and Π (0,10,0) could be identified. Instead the discordance between the two states appears to arise from different magnetic dipole–dipole coupling constants. The fine and hyperfine structure clearly reflect the presence of perturbations which limit the precision attainable for the derived hyperfine coupling constants. The coupling constants obtained for Π (0,10,0) are aN = 153.0(13), TaaN = −39.5(33), TccN = −37.4(19), ξaaN = 1.4(10), ξccN = −7.4(10), aH = 52.2(14), TaaH = 59.5(34), and TccH = −50.0(20), where all constants are in MHz and the uncertainties listed are 1 standard deviation. The magnetic constants for 14N are quite consistent with a simple sigma molecular orbital picture for the unpaired electron.

Microwave optical double resonance of NO 2 with a tunable cw dye laser : Spin-rotation and hyperfine interactions in the 2B2 excited electronic state

Various spin and hyperfine components of the 6 16 → 7 07 microwave transition in the 2 B 2 electronic excited state were observed by microwave optical double-resonance spectroscopy using a tunable cw dye laser near 593 nm. Spin splittings and the hyperfine structure of two levels were precisely determined. Spin-rotation and hyperfine interactions in the 2 B 2 state are discussed using these and the previously reported results on the 8 18 → 9 09 transition. From the hyperfine splittings of the K a = 0, N = 7 and 9 levels, a value for the Fermi contact interaction constant, (0) I , of ∼50 MHz was determined.

Microwave optical double resonance and continuous wave dye laser excitation spectroscopy of NO 2: Rotational assignment of the K = 0−4 subbands of the 593 nm band

A rotational assignment of approximately 80 lines with K a ′ = 0, 1, 2, 3, and 4 has been made of the 593 nm 2A 1 → 2B 2 band of NO 2 using cw dye laser excitation and microwave optical double-resonance spectroscopy. Rotational constants for the 2 B 2 state were obtained as A = 8.52 cm −1, B = 0.458 cm −1, and C = 0.388 cm −1. Spin splittings for the K a ′ = 0 excited state levels fit a simple symmetric top formula and give (ϵ bb + ϵ cc) 2 = −0.0483 cm −1 . Spin splittings for K a ′ = 1 ( N′ even) are irregular and are shown to change sign between N′ = 6 and 8. Assuming that the large inertial defect of 4.66 amu Å 2 arises solely from A, a structure for the 2 B 2 state is obtained which gives r (NO) = 1.35 A ̊ and an ONO angle of 105°. Alternatively, weighting the three rotational constants equally gives r = 1.29 A ̊ and θ = 118°.

Quadrupole fine structure in MODR spectroscopy and the determination of the absolute signs of the ZF parameters of excited triplet states. MODR spectrum of the 3A′ state of 1-bromonaphthalene in durene

We report measurements of the complete orientational dependence of the 3 cm microwave-optical double resonance (MODR) spectrum of the lowest 3(π,π*) state of 1-bromonaphthalene (1BN) in a durene host crystal at liquid helium temperatures. An analysis of the high-field spin Hamiltonian of triplet states containing quadrupolar nuclei shows that both the absolute signs and magnitudes of each of the zero-field (ZF) parameters as well as the principal values of the g, quadrupole, and hyperfine tensors can be determined using MODR techniques. For 3A′ 1BN, we find X/hc = +0.0434 cm−1, Y/hc = +0.0229 cm−1, Z/hc = −0.0663 cm−1, gxx = 2.003, gyy = 2.002, and gzz = 1.994. A comparison of these values with those obtained for 3B2u naphthalene suggests that the ZF scheme of the lowest triplet state of 1BN is modified by spin-orbit coupling with higher excited states, principally in the triplet manifold.

Microwave optical double resonance spectroscopy with a cw dye laser: BaO X1Σ and A1Σ

A tunable, single frequency, continuous wave, dye laser has been used to optically pump various lines of the BaO A 1Σ-X 1Σ electronic transition. Microwave optical double resonance (MODR) spectra are recorded as changes in the intensity of dye laser induced photoluminescence. Fourteen microwave rotational transitions in the X 1Σ (ν = 0,1) and A 1Σ (ν = 0–5) states of 138Ba16O and one transition in the A 1Σ (ν = 1) state of 137Ba16O have been observed. Partially deperturbed rotational constants obtained for BaO A 1Σ are B(ν) = 0.25832(2) − 0.001070(5) (ν + 1/2) cm−1. Two physical models are described which account for microwave optical double resonance effects in the strong (nonlinear) and weak (linear) optical pumping limits. Observed changes in photoluminescence polarization caused by excited state microwave transitions are predicted by a semiclassical transition dipole model. A three level steady state kinetic treatment of microwave optical double resonance indicates that the BaO MODR transitions reported in this paper are observed near the strong optical pumping limit. It is shown that for most allowed transitions in diatomic molecules a 100 mW single frequency, dye laser is sufficiently intense to significantly deplete rotational levels of the electronic ground state with respect to neighboring rotational levels and to cause the populations of the depleted ground state and optically pumped excited state levels to become comparable.

Microwave Optical Double Resonance Spectroscopy of BaO

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