Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

The Journal of Chemical Physics

Optogalvanic spectroscopy of two-photon dissociation of Tl2 at 532 nm producing large population inversion between Tl(7 2S1/2) and (6 2P3/2) states

Athar S. Naqvi

Published Mar 1, 1985• 7 citations
Publisher

Abstract

This paper reports the first time achievement of large population inversion between thallium 7 2S1/2 and 6 2P3/2 states through two-photon dissociation of pure Tl2 molecules. The second harmonic of a Nd–YAG laser at 532 nm is used to cause two-photon absorption in Tl2 from ground state Ou− to the repulsive state associated with the atomic 7 2S and 6 2P1/2 states. The relative population of the product atomic species is determined by using a tunable dye laser pumped by the third harmonic of a Nd–YAG laser. The dye laser beam focused for complete spatial and temporal overlap with the photodissociaiton pulse excites the product states to known atomic Rydberg states with subsequent ion detection. Prompt population inversion amounting to 100% is achieved. It is shown that photodissociation transition is mediated through predissociation of the upper bound state to a repulsive state correlated with Tl(7 S1/2) in the region of large internuclear separation.

DOI
10.1063/1.448314

Related papers

Optogalvanic spectroscopy of two-photon dissociation of Tl/sub 2/ at 532 nm producing large population inversion between Tl(7 /sup 2/S/sub 1/2/) and (6 /sup 2/P/sub 3/2/) states

Athar S. Naqvi

•Mar 1, 1985•0 citations

Efficiency studies of the thallium anti-Stokes Raman laser

J. C. White, Don O. Henderson

Selective photodissociation of TlCl and TlI using 248 nm radiation from a KrF* excimer laser has been used to create a Tl* (6p^{2}P\deg_{3/2}) metastable state population inversion. Stimulated anti-Stokes Raman emission at 376 nm has been observed using a 532 nm pump laser. Output power at the anti-Stokes wavelength and conversion efficiencies are reported.

IEEE Journal of Quantum Electronics•Jun 1, 1982•12 citations

Population and nonlinear polarization coherent changes on Raman transition due to two-photon pulse excitation

S. V. Anikeev, V. N. Kulyasov, Viacheslav B. Morozov +2 more

Population and third order nonlinear polarization coherent changes on Raman electronic transition of thallium atoms excited by a couple of 30 ps pulses of dye- and Nd:YAG lasers were observed. Collimated exciting and probing beams propagated through a heated cell of one centimeter length with thallium vapor. Population and nonlinear polarization dependences as functions of exciting pulses energy product were monitored using permanently delayed probing pulses.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Mar 15, 1999•0 citations

Focusing and defocusing of a near-resonant dye laser beam by photodissociation-produced Tl atoms

Jie Zhang, Terence A. King

A new optical effect showing focusing and defocusing of a near-resonant dye laser beam in Tl atomic vapour produced by photodissociation is reported. The effect is attributed to wavefront distortion of the dye laser beam, caused by Tl vapour number density gradient produced via an inhomogeneous intensity distribution of the dissociation KrF excimer laser beam, and the anomalous dispersion of Tl atoms near the resonance of the 6 2 P 3/2 -7 2 S 1/2 transition.

Journal of Physics B Atomic Molecular and Optical Physics•May 14, 1990•0 citations

Picosecond standoff multiphoton detection of gas phase species: initial results

Jerald B. Johnson, Kevin Lyon, William D. Murry +2 more

In the implementation of laser-induced fluorescence (LIF) for the detection of vapor-phase organic compounds that accompany hazardous materials, multiphoton excitation offers a significant advantage over single photon methods. In particular, if the absorption spectra of unwanted background molecules overlap that of the target molecule, single photon LIF is plagued by false positives. Multiphoton methods alleviate this difficulty by requiring that the target molecule be in resonance with multiple molecular transitions. A promising multiphoton method is stimulated Raman adiabatic passage (STIRAP). This method involves a counterintuitive sequence of laser pulses which is capable of transferring 100% of the target molecules to the desired excited state from which fluorescence is to be observed. As a precursor to more complex molecules, we demonstrate the STIRAP technique on sodium vapor using the 3p (2P1/2) ← 3s (2S1/2) and 5s (2S1/2) ← 3p (2P1/2) transitions. This is the first time STIRAP has been achieved on a vapor using picosecond lasers. We produced light to couple the states using two synchronously pumped OPG/OPAs (pumped by the 355 nm light from a picosecond YAG). We measured the fluorescence from the 5s state to both 3p states (2P1/2, 2P3/2) and from both 3p states to the 3s state with monochromator using a gated CCD to eliminate Rayleigh scattered light. Our results indicate a four to five-fold increase in the transfer efficiency to the 5s state when the laser pulse that couples the 3p and 5s states precedes the laser pulse tuned to the 3p ← 3s transition.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Mar 6, 2008•2 citations

DISSOCIATIVE EXCITATION SPECTROSCOPY OF $Cs_{2}: Cs_{2} + \gamma \to Cs_{2}{^{*}} \to Cs(6^{2}S) + Cs(5^{2}D)$

Jon A. Anderson, C. B. Collins, Pablo A. Vicharelli

A new method for studying dissociative molecular states, complementary to standard spectroscopy techniques, is discussed and its application to the specific case of $Cs_{2}$ is reported. Previous multi-photon ionization $experiments^{1,2}$ revealed the existence of hybrid absorption resonance, in which one photon causes a molecular transition to a dissociative state and a second photon is absorbed by one of the resulting dissociation fragments. The method of dissociation excitation spectroscopy uses two synchronized pulsed lasers to sequentially excite a dissociative molecular state and then detect the dissociation fragments through atomic excitation followed by collisional ionization. By scanning the wavelength of the laser probing the molecule it is possible to obtain a spectrum giving the relative probability that a specific dissociation product will be formed after photo-absorption in the molecule. The dissociation excitation spectrum, including the fine-structure branching ratio, has been obtained for the case \\[ Cs_{2} + \\gamma \\rightarrow Cs_{2}^{*} \\rightarrow Cs(6^{2}S_{1/2}) + Cs(5^{2}D_{3/2,5/2}) \\] over the wavelength region 4575-6050 $\\AA$. This spectrum shows marked similarities to the standard absorption spectrum of $Cs_{2}$. The implications for the molecular potentials of $Cs_{2}$ will be discussed.

•Jan 1, 1979•0 citations
This paper reports the first time achievement of large population inversion between thallium 7 2S1/2 and 6 2P3/2 states through two-photon dissociation of pure Tl2 molecules. The second harmonic of a Nd–YAG laser at 532 nm is used to cause two-photon absorption in Tl2 from ground state Ou− to the repulsive state associated with the atomic 7 2S and 6 2P1/2 states. The relative population of the product atomic species is determined by using a tunable dye laser pumped by the third harmonic of a Nd–YAG laser. The dye laser beam focused for complete spatial and temporal overlap with the photodissociaiton pulse excites the product states to known atomic Rydberg states with subsequent ion detection. Prompt population inversion amounting to 100% is achieved. It is shown that photodissociation transition is mediated through predissociation of the upper bound state to a repulsive state correlated with Tl(7 S1/2) in the region of large internuclear separation.
In the implementation of laser-induced fluorescence (LIF) for the detection of vapor-phase organic compounds that accompany hazardous materials, multiphoton excitation offers a significant advantage over single photon methods. In particular, if the absorption spectra of unwanted background molecules overlap that of the target molecule, single photon LIF is plagued by false positives. Multiphoton methods alleviate this difficulty by requiring that the target molecule be in resonance with multiple molecular transitions. A promising multiphoton method is stimulated Raman adiabatic passage (STIRAP). This method involves a counterintuitive sequence of laser pulses which is capable of transferring 100% of the target molecules to the desired excited state from which fluorescence is to be observed. As a precursor to more complex molecules, we demonstrate the STIRAP technique on sodium vapor using the 3p (2P1/2) ← 3s (2S1/2) and 5s (2S1/2) ← 3p (2P1/2) transitions. This is the first time STIRAP has been achieved on a vapor using picosecond lasers. We produced light to couple the states using two synchronously pumped OPG/OPAs (pumped by the 355 nm light from a picosecond YAG). We measured the fluorescence from the 5s state to both 3p states (2P1/2, 2P3/2) and from both 3p states to the 3s state with monochromator using a gated CCD to eliminate Rayleigh scattered light. Our results indicate a four to five-fold increase in the transfer efficiency to the 5s state when the laser pulse that couples the 3p and 5s states precedes the laser pulse tuned to the 3p ← 3s transition.
DISSOCIATIVE EXCITATION SPECTROSCOPY OF Cs2:Cs2+γ→Cs2∗→Cs(62S)+Cs(52D)Cs_{2}: Cs_{2} + \gamma \to Cs_{2}{^{*}} \to Cs(6^{2}S) + Cs(5^{2}D)Cs2​:Cs2​+γ→Cs2​∗→Cs(62S)+Cs(52D)
A new method for studying dissociative molecular states, complementary to standard spectroscopy techniques, is discussed and its application to the specific case of Cs2Cs_{2}Cs2​ is reported. Previous multi-photon ionization experiments1,2experiments^{1,2}experiments1,2 revealed the existence of hybrid absorption resonance, in which one photon causes a molecular transition to a dissociative state and a second photon is absorbed by one of the resulting dissociation fragments. The method of dissociation excitation spectroscopy uses two synchronized pulsed lasers to sequentially excite a dissociative molecular state and then detect the dissociation fragments through atomic excitation followed by collisional ionization. By scanning the wavelength of the laser probing the molecule it is possible to obtain a spectrum giving the relative probability that a specific dissociation product will be formed after photo-absorption in the molecule. The dissociation excitation spectrum, including the fine-structure branching ratio, has been obtained for the case \\[ Cs_{2} + \\gamma \\rightarrow Cs_{2}^{*} \\rightarrow Cs(6^{2}S_{1/2}) + Cs(5^{2}D_{3/2,5/2}) \\] over the wavelength region 4575-6050 AA\\AAAA. This spectrum shows marked similarities to the standard absorption spectrum of Cs2Cs_{2}Cs2​. The implications for the molecular potentials of Cs2Cs_{2}Cs2​ will be discussed.