Transitions Of Molecular Iodine Research Articles

Laser light sources for space-based gravitational wave detectors

This contribution summarizes recent progress in the development of diode-pumped Nd:YAG lasers suited for applications in laser-based metrology. Applying an unstable resonator design to a monolithic ring laser, 2 W single-frequency output power in a diffraction-limited beam is generated. Injection locking was used to increase the available power even further. Finally, techniques to improve the free-running lasers intensity and frequency stability are demonstrated. Low intensity noise is accomplished by application of an electronic feedback loop. Low frequency noise is achieved by stabilization onto a hyperfine transition of molecular iodine.

Hyperfine structure and absolute frequency determination of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of [formula omitted] near 532 nm

Hyperfine structures of the R(1 2 1)35-0 and P(1 4 2)37-0 transitions of molecular iodine at the blue end of the tuning range of a frequency-doubled Nd:YAG laser are measured by using two I 2-stabilized lasers. The absolute frequencies of the observed transitions are determined by a frequency link to an optical frequency reference (the R(5 6)32-0:a 10 hyperfine transition), using an optical frequency comb generator. The observed hyperfine transitions are good frequency references for both frequency-doubled Nd:YAG and Nd:YVO 4 lasers in the 532 nm region. High-accurate hyperfine constants are obtained for the P(1 4 2)37-0 transition by fitting the measured hyperfine splittings to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions.

Sub-Doppler molecular-iodine transitions near the dissociation limit (523-498 nm): errata

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Wang-Yau Cheng, Lisheng Chen, Tai Hyun Yoon, John L. Hall, and Jun Ye, "Sub-Doppler molecular-iodine transitions near the dissociation limit (523-498 nm): errata," Opt. Lett. 27, 1076-1076 (2002) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Vibration dependence of the tensor spin–spin and scalar spin–spin hyperfine interactions by precision measurement of hyperfine structures of ^127I_2 near 532 nm

Hyperfine structures of the R(87)33-0,R(145)37-0, and P(132)36-0 transitions of molecular iodine near 532 nm are measured by observing the heterodyne beat-note signal of two I2-stabilized lasers, whose frequencies are bridged by an optical frequency comb generator. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions, with an accuracy of ∼720 Hz. High-accurate hyperfine constants are obtained from this fit. Vibration dependences of the tensor spin–spin and scalar spin–spin hyperfine constants are determined for molecular iodine, for the first time to our knowledge. The observed hyperfine transitions are good optical frequency references in the 532-nm region.

Sub-Doppler molecular-iodine transitions near the dissociation limit (523–498 nm)

A widely tunable and high-resolution spectrometer based on a frequency-doubled Ti:sapphire laser was used to explore sub-Doppler transitions of iodine molecules in the wavelength range 523-498 nm. The wavelength dependence of the hyperfine transition linewidth of iodine was mapped out in this region, and the narrowest linewidth was ~4 kHz near 508 nm. The hyperfine-resolved patterns were found to be largely modified toward the dissociation limit. The observed excellent signal-to-noise ratio should lead to high-quality optical frequency standards that are better than those of the popular 532-nm system.

Rotation dependence of the excited-state electric quadrupole hyperfine interaction by high-resolution laser spectroscopy of ^127I_2

Hyperfine structures of the R(58)32–0,P(55)32–0, and P(104)34–0 transitions of molecular iodine near 532 nm are measured by heterodyne beating of two I2-stabilized lasers. The measured hyperfine splittings are fitted to a four-term Hamiltonian, which includes the electric quadrupole, spin–rotation, tensor spin–spin, and scalar spin–spin interactions, with an accuracy of ∼600 Hz for the R(58)32–0 and P(55)32–0 transitions. Highly accurate hyperfine constants are obtained from this fit. The rotation dependence of the excited state (the B state, v′=32) electric quadrupole constant eQq′ is found to be eQq′(J)=-544.049(14)-0.0002110(43)J(J+1) MHz. The observed hyperfine transitions are good candidates for an optical frequency reference in the 532-nm region.

Hyperfine structures of the R(122)35-0 and P(84)33-0 transitions of [formula omitted] near 532 nm

Hyperfine structures of the R(122)35-0 and P(84)33-0 transitions of molecular iodine near 532 nm are observed at the red end of the tuning range of the frequency-doubled Nd:YAG laser. Frequency separations between the hyperfine components are measured by observing the heterodyne beat between two I 2-stabilized lasers. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin-rotation, tensor spin–spin, and scalar spin–spin interactions, with an accuracy of about 660 Hz. A new empirical formula for the electric quadrupole constant as a function of the vibrational and rotational energies in the B state is proposed. The observed hyperfine transitions are good candidates for an optical frequency reference in the 532 nm region.

A Dense Grid of Reference Iodine Lines for Optical Frequency Calibration in the Range 595–655 nm

A dense grid of reference lines in the hyperfine structure of the B–X transitions of molecular iodine (127I2) is presented. Frequencies of 481 “t”-hyperfine components in 15 vibrational bands covering the wavelength range 595–655 nm were determined with an absolute accuracy of 1.0 MHz (1ς uncertainty). Spectra were obtained by Doppler-free saturation spectroscopy using a cw ring-dye laser of 1-MHz bandwidth. Center-of-gravity frequencies of rovibronic lines, determined by correcting for the calculated hyperfine shift, are included separately in a least-squares parametrization for each band. From the obtained molecular constants a prediction is made for all t-hyperfine components of the 15 bands covering 595–655 nm. Hence a dense grid of reference lines of 1 MHz (1ς) absolute accuracy is created, with a line in each interval of 1 cm−1 in the entire range. This spectral atlas of about 3400 lines may provide a useful calibration tool in many laboratories.

Development of a hybrid laser system: toward an improved working standard at 633 nm

Aiming to improve the working standard at 633 nm, we developed a hybrid laser system, in which a visible diode laser was injection locked by a He-Ne laser. The hybrid laser system can produce single-mode radiation with an output power of more than 20 mW in a compact setup. In the preliminary experiment, two hybrid laser systems were stabilized to the P(33) 6-3 transition of molecular iodine using the 3f-modulation technique and a stability of 4.8/spl times/10/sup -13/ was obtained.

Frequency stabilization of a diode laser to Doppler-free spectrum of molecular iodine at 633 nm

We report on frequency stabilization of a diode laser to the hyperfine components of the P(33) 6-3 and R(127) 11-5 transitions of molecular iodine at the He-Ne laser wavelength of 633 nm. Single frequency operation and wavelength control of the diode laser in a compact form is obtained by employing weak optical feedback from an integrated microlens. The diode laser driven by an ultra low noise current supply provides nearly shot noise limited detection. A relative frequency stability of 5×10 −12 is achieved at an integration time of 100 s. Harmonic distortion of the modulated output of the diode laser due to spurious optical feedback is considered to be the main effect limiting the day-to-day frequency reproducibility of 5×10 −11.

Frequency doubling of a fibre-amplified 1083 nm DBR laser

A good frequency standard is required at 1083 nm for measurements on the fine structure of helium and of the fine structure constant. Several milliwatts of CW frequency-doubled light offers the prospect of stabilisation to a Doppler-free hyperfine transition in molecular iodine. The 1083 nm emission of an extended-cavity DBR diode laser has been amplified using an ytterbium-doped fibre amplifier, and applied to a type-I phase matched Mg:LiNbO3 crystal in a high-Q fundamental-resonant cavity for frequency doubling. The amplifier gain at 1083 nm under typical operating conditions was 13.8 dB, with a coherent output power up to 63 mW, limited by the maximum signal input power. The doubling cavity Q was , and about 70% of the incident power was coupled in. The maximum 2nd-harmonic conversion efficiency exceeded 20% and provided an output power of 3.7 mW for making continuous frequency scans of up to 600 MHz in the green. An optical spectrum analyser at 541.5 nm showed fringes of 4.6 MHz full width half maximum, close to the instrumental width.

Amplitude noise and linewidth reduction of an Ar/sup +/ laser

Frequency modulation spectroscopy is used to frequency stabilize an Ar/sup +/ laser at 515 nm with respect to a commercial passive cavity. Two transducers, a slow and a fast one, are used. The fast transducer is also used to perform amplitude stabilization of a laser beam. Measured amplitude and frequency spectral noise densities are reported. A simplified scheme of the circuitry used to reduce amplitude noise is shown. Noise characteristics of the realized system are adequate to perform spectroscopy of hyperfine-structure transitions of molecular iodine.

Solvent-induced nonadiabatic transitions in iodine: An ultrafast pump–probe computational study

The solvent-induced electronic predissociation [B→a1g(3Π)] following an ultrafast X→B transition in molecular iodine is studied using a classical ensemble representation of Heisenberg’s equations of motion. An N electronic state quantum mechanical Hamiltonian is used to derive (coupled) equations of motion for the population (and the coherence) of the different electronic states as well as classicallike coupled equations for the nuclear dynamics (of both the molecule and the solvent) on each electronic state. The ultrafast excitation of the intermediate B state creates a coherent vibrational motion in this bound state. The localized nature of the solvent-induced B–a1g(3Π) coupling results in a steplike depletion of the excited B state population and hence in a bulletlike appearance of population on the dissociative a1g(3Π) state twice per vibrational period. The depletion of the B state population and the appearance of products on the a1g(3Π) state are discussed as a function of solvent density and polarizability. The magnitude of the nonadiabatic B–a1g(3Π) coupling depends both on the molecule–quencher separation and on the quencher’s polarizability. It is found that at all reduced densities the small Ar atom is the most effective quencher (when compared to either Kr and/or Xe). We attribute this unexpected trend to the local density of atoms around the solute molecule. For all the rare gas solvents the local density around the iodine molecule does not quite scale with the global one and there is an observed tendency for the solvent to cluster around the solute in a T-shaped configuration. It is this close-packed configuration that compensates for the smaller polarizability of the Ar atom and hence provides for a more effective quenching. These arguments are used to explain the experimental results which demonstrate that for a series of homologous alkanes the extent of predissociation scales with the length of the molecular chain although the global polarizability density remains roughly constant.

Second-order Zeeman effect of theX?B transition in molecular iodine

Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX(ν″ = 0,J″ = 13,15) →B(ν′ = 43,J′ = 12, 16) transition (λ = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X′ = 7.3 ± 1 × 10−34 J/Oe2) and theX(0) [χ″ = (0.6 ± 1) × 10−34 J/Oe2] states as well as the isotropic MS difference [χ′0 −χ″o = (2 ± 0.2) × 10−34 J/Oe2] was measured.

Absolute frequency of the molecular iodine transition R(56)32-0 near 532 nm

The absolute frequency of the hyperfine component a/sub 10/ in the transition R(56)32-0 of iodine has been measured using the D/sub 2/ line in Rb at 780 mm and an iodine-stabilized 633-nm He-Ne laser as references. This measurement provides a secondary frequency standard within the tuning range of a doubled Nd:YAG laser. The measured frequency of the a/sub 10/ component is 563 260 223.480 MHz /spl plusmn/70 kHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Direct observation of the second-order Stark effect of theX-B transition in molecular iodine

The second-order Stark shift of the components of the hyperfine structure of the transition1∑ g + (υ″ = 0,j″ = 13, 15) →3∏ ou + (υ′ = 43,j′ = 12, 16) (of molecular iodine have been studied by means of saturated absorption spectroscopy in an external cell with the I2 vapour located in an electric field. The anisotropic polarizabilities of the upper and lower levels together with the difference between the isotropic polarizabilities of the levels of the transition have been obtained.

The electronic transition dipole moment of the B+u→X+g transition in iodine

The electronic transition dipole moment of the B0+u→X0+g transition in molecular iodine has been determined in the range 2.633≤Rcentroid≤6.035 Å. We have measured a decrease of ‖μ̄e‖2 of about 4 orders of magnitude, perhaps the largest variation of ‖μ̄e‖2 yet observed in a molecule.

Direct observation of the anomalous zeeman effect at the X ? B transition of molecular iodine by the method of nonlinear laser spectroscopy

Direct observation of the magnetic structure of transitions in molecular iodine is first reported. Using the method of saturated absorption spectroscopy in an external cell with I2 vapour located in a longitudinal magnetic field we resolved the magnetic structure of the components of the hyperfine structure of the transition $${}^1\sum _g^ + (v^ = 0,{\text{j}}^ = 13,15) \to {}^3\prod _{ou}^ + (v^\prime = 43,{\text{j}}^\prime = 12,16).$$ The gyromagnetic constants of the upper and lower levels of the transition have been found. An estimation of the frequency shift of saturation resonances in the magnetic field has been made.

Study of relaxation of molecular iodine by the method of saturated absorption spectroscopy

The paper describes detailed experimental studies of the width, shape and shifts of saturated absorption resonances at the X(v″=0, j″=13)→B(v′=43, j′=12) transition of molecular iodine. Use of the geometry of oppositely travelling and unidirectional waves in the experiment and study of the luminescence decay under pulsed excitation allowed estimation of the cross-sections of elastic and inelastic scattering of I2 molecules on the upper and lower levels of transition. The observed nonlinear dependence of width and shift of the saturation resonance on iodine pressure is explained by the influence of elastic collisions with no phase mismatch.

Doppler-free optical multiplex spectroscopy with stochastic excitation

By using the concept of stochastic excitation, a multichannel optical spectrometer was developed with an inherent spectral resolution in the kilohertz domain. Stochastic optical fields are obtained by phase modulating a frequency-stabilized Ar+ laser with a pseudorandom binary sequence. This sequence is characterized by an autocorrelation time of 5 nsec, with a resulting excitation bandwidth of approximately 200 MHz. A signal related to an optical free-induction decay is obtained after cross correlating the response of the system with the time-delayed stochastic excitation sequence. The performance of the spectrometer was demonstrated by observing Doppler-free transitions of molecular iodine.