77 research outputs found
Narrowing of spectral lines beyond the natural or dephasing line width
Transient excitation and gated or delayed observation provides a narrowing of the inherent line width of the transition. Possible experimental one- and two-photon systems are discussed and the loss of signal with line narrowing is calculated. The general case of lines broadened by dephasing processes is treated. Contact is made with the line narrowing in recent Raman type experiments
Coherent control at its most fundamental: CEP-dependent electron localization in photodissoziation of a H2+ molecular ion beam target
Measurements and calculations of the absolute carrier-envelope phase (CEP)
effects in the photodissociation of the simplest molecule, H2+, with a 4.5-fs
Ti:Sapphire laser pulse at intensities up to (4 +- 2)x10^14 Watt/cm^2 are
presented. Localization of the electron with respect to the two nuclei (during
the dissociation process) is controlled via the CEP of the ultra-short laser
pulses. In contrast to previous CEP-dependent experiments with neutral
molecules, the dissociation of the molecular ions is not preceded by a
photoionization process, which strongly influences the CEP dependence.
Kinematically complete data is obtained by time- and position-resolved
coincidence detection. The phase dependence is determined by a single-shot
phase measurement correlated to the detection of the dissoziation fragments.
The experimental results show quantitative agreement with ab inito 3D-TDSE
calculations that include nuclear vibration and rotation.Comment: new version includes minore changes and adding the supp_material.pd
Manipulating ionization path in a Stark map: Stringent schemes for the selective field ionization in highly excited Rb Rydberg atoms
We have developed a quite stringent method in selectivity to ionize the low
angular- momentum () states which lie below and above the adjacent
manifold in highly excited Rb Rydberg atoms. The method fully exploits the
pulsed field-ionization characteristics of the manifold states in high
slew-rate regime: Specifically the low state below (above) the adjacent
manifold is firstly transferred to the lowest (highest) state in the manifold
via the adiabatic transition at the first avoided crossing in low slew-rate
regime, and then the atoms are driven to a high electric field for ionization
in high slew-rate regime. These extreme states of the manifold are ionized at
quite different fields due to the tunneling process, resulting in thus the
stringent selectivity. Two manipulation schemes to realize this method actually
are demonstrated here experimentally.Comment: 10 pages, 4 figure
Systematic observation of tunneling field-ionization in highly excited Rb Rydberg atoms
Pulsed field ionization of high- (90 150) manifold states in
Rb Rydberg atoms has been investigated in high slew-rate regime. Two peaks in
the field ionization spectra were systematically observed for the investigated
region, where the field values at the lower peak do not almost depend on
the excitation energy in the manifold, while those at the higher peak increase
with increasing excitation energy. The fraction of the higher peak component to
the total ionization signals increases with increasing , exceeding 80% at
= 147. Characteristic behavior of the peak component and the comparison
with theoretical predictions indicate that the higher peak component is due to
the tunneling process. The obtained results show for the first time that the
tunneling process plays increasingly the dominant role at such highly excited
nonhydrogenic Rydberg atoms.Comment: 8 pages, 5 figure
Effect of Residue Management, Row Spacing, and Seeding Rate on Winter Canola Establishment, Winter Survival, and Yield
Winter survival of canola (Brassica napus L.) is a challenge for producers using high-residue, no-tillage, or reduced-tillage systems. An innovative residue management system being developed by AGCO Corporation was compared to cooperating canola producers’ residue management and planting methods in wheat stubble. This series of on-farm experiments was conducted in 2014-2015 and 2015-2016 at ten locations in central and south-central Kansas. The AGCO treatments were 20- or 30-in. row spacing and three seeding rates (100,000, 150,000, and 200,000 seeds/a) for a total of six treatments. The producer treatment at each location included row spacing, seeding rate, and residue management practices preferred by that producer. Due to winter stand loss, only one of the six experiments planted in the fall of 2014 was harvested for yield in 2015. All four experiments planted in fall 2015 were harvested for yield in 2016. Fall stands usually differed in response to seeding rate and often were greater in 20-in. rows than in 30-in. rows. Spring stands were not as tightly correlated with seeding rate, but were consistently greater in narrow rows, regardless of seeding rate and residue management practices. Winter survival increased with reductions in seeding rate at most locations and was greater in 20-in. rows than in 30-in. rows at three of the five harvested locations. Yields were not affected by residue management, row spacing, or seeding rate at two of the five locations, including the location with yields surpassing 60 bu/a. At the other three locations, yields with the AGCO residue management system equaled or exceeded yields obtained with cooperator practices that typically included much greater seeding rates. Yields seldom responded to seeding rate, but when they did, yields tended to increase as seeding rate decreased
Line-narrowing transient Raman technique which resolves closely spaced hydrogen-bonded aggregates
An ultrafast coherent Raman spectroscopy with tunable excitation is presented. It is applied to the analysis of vibrational spectra of hydrogen-bonded aggregates of pyridine and methanol. Whereas the spontaneous Raman spectrum exhibits a broad and featureless band, the line-narrowed spectra reveal three distinct lines. The concentration dependence of these lines suggests an assignment to well-defined aggregates of different sizes
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