Molecular dissociation observed with an atomic wavepacket and parametric four-wave mixing

Senin, A. A.; Tran, H.; Gao, Ju; Lu, Zhanbin; Zhu, Changjun; Oldenburg, Amy L.; Allen, J. R.; Eden, J. G.

doi:10.1016/j.cplett.2003.09.075

Cited by 19 publications

(6 citation statements)

References 17 publications

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“…On the other hand, the signal to noise ratio of the FFT amplitude decreases with an increase in the Rb number density. Similar results observed by time-delayed PFWM are explained in terms of the dipole-dipole interaction resulting from the dissociation of Rb dimmers (i.e., an increased mean velocity and number density of Rb atoms and dissociation fragments of Rb dimers produced in the Rb cell hasten the dephasing process of the excited Rb atoms [3]). …”

supporting

confidence: 72%

“…With axially phase-matched PFWM, quantum beating at 608 cm-' in Rb was observed by monitoring a coherent signal at 420 nm [2]. Furthermore, the temporal evolution of quantum beating at 608 cm-' was employed as a unique detector to monitor the dissociation dynamics of diatomic molecules [3]. Optical six-wave mixing (SWM) is intriguing and has been studied in several alkali atomic vapor systems: sodium [4], potassium [5], lithium [6] and sodium-potassium mixtures [7].…”

mentioning

confidence: 99%

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Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Zhu

Senin

Eden

2005 Quantum Electronics and Laser Science Conference

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supporting

confidence: 72%

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confidence: 99%

Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Zhu

Senin

Eden

2005 Quantum Electronics and Laser Science Conference

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“…In that vein, Shen et al [18] recently reported the observation in the vapour phase of many-body, dipole-dipole interactions, detected through the appearance of sidebands in the Fourier spectra of Rb wavepackets. This result opens an avenue to the direct observation of molecular dissociation, [14] the subject of this paper. Fragments of dissociation, approaching an atomic wavepacket, perturb the amplitude and phase of quantum beating in the atom (through the dipole-dipole interaction) which produces by PFWM a macroscopic response from the medium in the form of a coherent, modulated beam of ultraviolet or visible radiation.…”

Section: Detection Of Molecular and Atomic Wavepackets: A Brief Reviewmentioning

confidence: 72%

“…Recent emphasis on the photodissociation of diatomic molecular ions in intense optical fields, for example, has yielded two-dimensional momentum projections for the neutral photofragments of H + 2 and Ar + 2 , [11,12] and experiments investigating HeH + photodissociation at 32 nm observed both the kinetic energy and fragmentation angle of neutral He by event imaging. [13] In 2003, Senin et al [14] reported the observation of the dissociation of an electronically excited molecule by monitoring the temporal behaviour of atomic wavepackets with a coherent nonlinear optical process such as parametric four-wave mixing [15,16].…”

Section: Introductionmentioning

confidence: 99%

Molecular dissociation and nascent product state distributions detected with atomic wavepacket interferometry and parametric four-wave mixing: Rb₂predissociation observed by quantum beating in Rb at 18.2 THz

Yan¹,

Senin²,

Ricconi³

et al. 2008

J. Phys. B: At. Mol. Opt. Phys.

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Dissociation of a diatomic molecule and the excited-state distribution of the nascent atomic fragments can be detected and characterized by atomic wavepacket interferometry and a coherent nonlinear optical process, such as parametric four-wave mixing (PFWM), in ultrafast pump–probe experiments. Underlying these experiments is a reliance on atom–atom interaction to alter the properties of an atomic wavepacket which, in turn, impacts the phase and amplitude of a coherent optical signal. Specifically, quantum beating in the atomic species provides a sensitive, in situ probe of molecular dissociation by detecting approaching dissociation fragments through long-range dipole–dipole interaction. The resulting influence of this interaction on the amplitude and phase of the quantum beating is observed in temporal or Fourier domains by probing the wavepacket by interferometry and PFWM with 100–150 fs laser pulses. The wavepacket thus serves as a detector of molecular dissociation fragments and the dynamics of atom–atom interactions are converted into the macroscopic domain by the PFWM signal and idler waves. Femtosecond pump–probe experiments are described in which the predissociation of electronically excited Rb2 states in the ∼24 000–28 000 cm−1 interval, and the distribution of nascent atomic fragments into Rb excited states (7s, 5d, 6s, 4d and 5p) spanning an energy range >1.25 eV, have been observed in Rb vapour with atomic number densities of ∼6 × 1013–3 × 1017 cm−3. Quantum beating at 18.2 THz (corresponding to the Rb 7s–5dJ (J = 5/2) energy defect of ∼608 cm−1) is superimposed onto the axially phase matched PFWM signal wave generated at λS ∼ 420 nm (Rb 62PJ → 52S1/2 transitions) and recovered by Fourier analysis of the signal wave intensity as the pump–probe time delay (Δt) is scanned. The dominant exit channels for Rb2 predissociation are found to be sensitive to the interval of internuclear separation R in which the molecular wavepacket, produced by the pump pulse through two-photon association of Rb–Rb collision pairs, is localized. Generating Rb2 wavepackets on 3Λu (Λ = Σ, Δ) potential surfaces at large R (∼7–9 Å) favours the Rb 7s and 5d dissociation channels. In contrast, producing dimer wavepackets localized in the R ∼ 3–4 Å region suppresses Rb (7s, 5d) generation and favours the production of Rb atomic fragments (primarily 5p) with less internal energy, but maximum velocities of ∼15–20 Å ps−1. Laser excitation spectroscopy on the nanosecond time scale suggests that the (3)3Δu and (7)3Σ+u states of Rb2 (correlated with Rd (5d) + Rb (6s) in the separated atom limit), and possibly a 3Σ+u state derived from the Rb (7p) + Rb (5s) asymptote, are populated by two-photon absorption of Rb–Rb ground-state collision pairs and predissociation of these levels provides the excited atomic fragments subsequently detected by atomic wavepackets. The data presented here demonstrate the observation of the molecular dissociation transient and the determination of the nascent statistical distribution of atomic product states in ...

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“…With axially phase-matched PFWM, quantum beating in Rb at 18.2 THz, corresponding to the 7s-5d (J�S/2) energy defect, was observed by monitoring the coherent signal at 420 nm. The temporal evolution of quantum beating at 18.2 THz was employed as a unique tool to observe the dissociation dynamics of diatomic molecules [2].…”

mentioning

confidence: 99%

Observation of quantum beating at 18.2 THz in Rb by parametric six-wave mixing

Zhu

Senin

Gao

et al.

The 17th Annual Meeting of the IEEELasers and Electro-Optics Society, 2004. LEOS 2004.

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Parametric Six-Wave Mixing is observed in Rb and the modulation of 1365 nm signal at 18.2 THz is detected by observing the coherent radiation at 492 nm produced by summing the pump and the signal.We have shown recently that the behavior of an atomic wavepacket can be observed by pump-probe experiments in which the wavepacket is interrogated by parametric four-wave mixing (PFWM) [1]. With axially phase-matched PFWM, quantum beating in Rb at 18.2 THz, corresponding to the 7s-5d (J�S/2) energy defect, was observed by monitoring the coherent signal at 420 nm. The temporal evolution of quantum beating at 18.2 THz was employed as a unique tool to observe the dissociation dynamics of diatomic molecules [2].Of particular interest to optoelectronics in the visible and near infrared (lR), however, is the fact that the signal wave is modulated at 18.2 THz. In this paper, we report the observation of parametric Six-Wave Mixing (SWM) in Rb as well as the observation of quantum beating at 18.2 THz by sum frequency mixing. This process has intriguing applications for modulating visible and near IR coherent radiation at precisely-specified frequencies. Figure 1 shows the Rb energy levels involved in the parametric SWM process. Of particular interest is the coherent signal wave at 1365 nm that is associated with the 62S1I2 � 52p3/2 transition of Rb. The experiments involved exciting Rb vapor with a pair of � 150 fs pulses produced by a Ti:sapphire oscillator/regenerative amplifier system operating at 1 kHz.The time delay between the pulses was computer-controlled with a Michelson interferometer. Both the pump and probe pulses possess vertically linear polarization. The pump-probe configuration, combined with parametric SWM, has the advantages of fs temporal resolution and a detection mechanism (coherent radiation at the signal frequency) that offers an extraordinary SIN ratio. A coherent superposition of the Rb 7s and 5d states is prepared by the pump pulse (centered at 770 nm) through two-photon absorption in Rb vapor. A coherent signal wave at 1365 nm is subsequently produced by two parametric SWM processes, 5 2 S1/ 2 �� 7 2 S1/ 2 � 6 2 p3/ 2 � 6 2 S1/ 2 � 5 2 p3/ 2 � 5 2 S1/ 2 and 5 2 S1/ 2 �� 5 2 Ds/ 2 � 6 2 p3/ 2 � 6 2 S1/ 2 � 5 2 p3/ 2 � 5 2 S1/ 2 . A second superposition of the 7s and 5d states is produced by the probe pulse, delayed in time with respect to the pump by L'lt. The emission at 1365 nm and the laser radiation at 770 nm are focused into a Lil03 crystal, which generates a sum frequency signal at 492 nm, as shown in Figure 2.The intensity of the sum frequency signal at 492 nm is recorded as a function of L'lt. Interference between the 7s and 5d states results in a quantum beating at 18.2 THz, which is embedded in the 1365 nm emission, and hence in the sum frequency signal at 492 nm. The quantum beating can be recovered through the Fast Fourier Transform (FFT) of the variation of the sum frequency signal with L'lt. Figure 3 shows data representative of these experiments in which the relative 492 nm signal intensit...

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Molecular dissociation observed with an atomic wavepacket and parametric four-wave mixing

Cited by 19 publications

References 17 publications

Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Molecular dissociation and nascent product state distributions detected with atomic wavepacket interferometry and parametric four-wave mixing: Rb₂predissociation observed by quantum beating in Rb at 18.2 THz

Observation of quantum beating at 18.2 THz in Rb by parametric six-wave mixing

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Molecular dissociation observed with an atomic wavepacket and parametric four-wave mixing

Cited by 19 publications

References 17 publications

Parametric Six-Wave Mixing and Quantum Beating at 608 cm&gt;sup&lt;-1&gt;/sup&lt;in Rb

Parametric Six-Wave Mixing and Quantum Beating at 608 cm&gt;sup&lt;-1&gt;/sup&lt;in Rb

Molecular dissociation and nascent product state distributions detected with atomic wavepacket interferometry and parametric four-wave mixing: Rb2predissociation observed by quantum beating in Rb at 18.2 THz

Observation of quantum beating at 18.2 THz in Rb by parametric six-wave mixing

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Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Parametric Six-Wave Mixing and Quantum Beating at 608 cm>sup<-1>/sup<in Rb

Molecular dissociation and nascent product state distributions detected with atomic wavepacket interferometry and parametric four-wave mixing: Rb₂predissociation observed by quantum beating in Rb at 18.2 THz