Temperature dependence of collisional broadening and shift for the Kr 4 p 6 S 01→5 p [3/2] 2 electronic transition

Temperature scaling of collisional broadening parameters for krypton (absorber)$4p6S01→<#comment/>5p[3/2]2$electronic transition centered at 107.3 nm in the presence of major combustion species (perturber) is investigated. The absorption spectrum in the vicinity of the transition is obtained from the fluorescence due to the two-photon excitation scan of krypton. Krypton was added in small amounts to major combustion species such as$CH4$,$CO2$,$N2$, and air, which then heated to elevated temperatures when flowed through a set of heated coils. In a separate experimental campaign, laminar premixed flat flame product mixtures of methane combustion were employed to extend the investigations to higher temperature ranges relevant to combustion. Collisional full width half maximum (FWHM) ($wC$) and shift ($δ<#comment/>C$) were computed from the absorption spectrum by synthetically fitting Voigt profiles to the excitation scans, and their corresponding temperature scaling was determined by fitting power-law temperature dependencies to the$wC$and$δ<#comment/>C$data for each perturber species. The temperature exponents of$wC$and$δ<#comment/>C$for all considered combustion species (perturbers) were$−<#comment/>0.73$and$−<#comment/>0.6$, respectively. Whereas the temperature exponents of$wC$are closer to more »

Authors:
; ;
Publication Date:
NSF-PAR ID:
10133660
Journal Name:
Applied Optics
Volume:
59
Issue:
5
Page Range or eLocation-ID:
Article No. 1438
ISSN:
1559-128X; APOPAI
Publisher:
Optical Society of America
1. Pressure scaling of collisional broadening parameters of krypton (absorber)$4p6S01→<#comment/>→<#comment/>5p[3/2]2$transition centered at 107.3 nm in the presence of nitrogen$N2$(perturber) is investigated. The absorption spectrum in the vicinity of the transition is obtained from the two-photon excitation scan of krypton in the presence of the perturber at different prescribed pressures varying from a few torrs to 10 atm. The absorption spectra reveal noticeable asymmetry at atmospheric pressure, and the asymmetry becomes increasingly pronounced with pressure; however, the absorption spectra at sub-atmospheric pressures tested are symmetric. The absorption spectra are fitted with synthetic asymmetric Voigt profiles across all pressures, wherein the asymmetry parameter is varied to capture the asymmetry at different pressures. The collisional shift ($δ<#comment/>C$), the symmetric equivalent collisional full width at half maximum ($wC,0$), and the asymmetry parameter ($a$) are determined from the synthetic fits at various pressures. All the parameters are observed to vary linearly with pressure over the entire range of the pressure values tested. The mechanisms that cause the asymmetry in the absorption spectra are also discussed.
2. The mid-IR spectroscopic properties of$Er3+$doped low-phonon$CsCdCl3$and$CsPbCl3$crystals grown by the Bridgman technique have been investigated. Using optical excitations at$∼<#comment/>800nm$and$∼<#comment/>660nm$, both crystals exhibited IR emissions at$∼<#comment/>1.55$,$∼<#comment/>2.75$,$∼<#comment/>3.5$, and$∼<#comment/>4.5µ<#comment/>m$at room temperature. The mid-IR emission at 4.5 µm, originating from the$4I9/2→<#comment/>4I11/2$transition, showed a long emission lifetime of$∼<#comment/>11.6ms$for$Er3+$doped$CsCdCl3$, whereas$Er3+$doped$CsPbCl3$exhibited a shorter lifetime of$∼<#comment/>1.8ms$. The measured emission lifetimes of the$4I9/2$state were nearly independent of the temperature, indicating a negligibly small nonradiative decay rate through multiphonon relaxation, as predicted by the energy-gap law for low-maximum-phonon energy hosts. The room temperature stimulatedmore »
3. Electro-optic quantum coherent interfaces map the amplitude and phase of a quantum signal directly to the phase or intensity of a probe beam. At terahertz frequencies, a fundamental challenge is not only to sense such weak signals (due to a weak coupling with a probe in the near-infrared) but also to resolve them in the time domain. Cavity confinement of both light fields can increase the interaction and achieve strong coupling. Using this approach, current realizations are limited to low microwave frequencies. Alternatively, in bulk crystals, electro-optic sampling was shown to reach quantum-level sensitivity of terahertz waves. Yet, the coupling strength was extremely weak. Here, we propose an on-chip architecture that concomitantly provides subcycle temporal resolution and an extreme sensitivity to sense terahertz intracavity fields below 20 V/m. We use guided femtosecond pulses in the near-infrared and a confinement of the terahertz wave to a volume of$VTHz∼<#comment/>10−<#comment/>9(λ<#comment/>THz/2)3$in combination with ultraperformant organic molecules ($r33=170pm/V$) and accomplish a record-high single-photon electro-optic coupling rate of, 10,000 times higher than in recent reports of sensing vacuum field fluctuations in bulk media. Via homodyne detection implemented directly on chip, the interaction results into an intensity modulation of the femtosecond pulses. The single-photon cooperativity is$C0=1.6×<#comment/>10−<#comment/>8$, and the multiphoton cooperativity is$C=0.002$at room temperature. We show$><#comment/>70dB$dynamic range in intensity at 500 ms integration under irradiation with a weak coherent terahertz field. Similar devices could be employed in future measurements of quantum states in the terahertz at the standard quantum limit, or for entanglement of subsystems on subcycle temporal scales, such as terahertz and near-infrared quantum bits.
4. We report on spectroscopic measurements on the$4f76s28S7/2∘<#comment/>→<#comment/>4f7(8S∘<#comment/>)6s6p(1P∘<#comment/>)8P9/2$transition in neutral europium-151 and europium-153 at 459.4 nm. The center of gravity frequencies for the 151 and 153 isotopes, reported for the first time in this paper, to our knowledge, were found to be 652,389,757.16(34) MHz and 652,386,593.2(5) MHz, respectively. The hyperfine coefficients for the$6s6p(1P∘<#comment/>)8P9/2$state were found to be$A(151)=−<#comment/>228.84(2)MHz$,$B(151)=226.9(5)MHz$and$A(153)=−<#comment/>101.87(6)MHz$,$B(153)=575.4(1.5)MHz$, which all agree with previously published results except for A(153), which shows a small discrepancy. The isotope shift is found to be 3163.8(6) MHz, which also has a discrepancy with previously published results.
5. An optical parametric oscillator (OPO) is developed and characterized for the simultaneous generation of ultraviolet (UV) and near-UV nanosecond laser pulses for the single-shot Rayleigh scattering and planar laser-induced-fluorescence (PLIF) imaging of methylidyne (CH) and nitric oxide (NO) in turbulent flames. The OPO is pumped by a multichannel, 8-pulse Nd:YAG laser cluster that produces up to 225 mJ/pulse at 355 nm with pulse spacing of 100 µs. The pulsed OPO has a conversion efficiency of 9.6% to the signal wavelength of$∼<#comment/>430nm$when pumped by the multimode laser. Second harmonic conversion of the signal, with 3.8% efficiency, is used for the electronic excitation of the A-X (1,0) band of NO at$∼<#comment/>215nm$, while the residual signal at 430 nm is used for direct excitation of the A-X (0,0) band of the CH radical and elastic Rayleigh scattering. The section of the OPO signal wavelength for simultaneous CH and NO PLIF imaging is performed with consideration of the pulse energy, interference from the reactant and product species, and the fluorescence signal intensity. The excitation wavelengths of 430.7 nm and 215.35 nm are studied in a laminar, premixed–air flame. Single-shot CH and NO PLIF and Rayleigh scatter imaging is demonstrated in a turbulent$CH4−<#comment/>H2−<#comment/>NH3$diffusion flame using a high-speed intensified CMOS camera. Analysis of the complementary Rayleigh scattering and CH and NO PLIF enables identification and quantification of the high-temperature flame layers, the combustion product zones, and the fuel-jet core. Considerations for extension to simultaneous, 10-kHz-rate acquisition are discussed.