scholarly journals Saturation in the principal (excited) channel of four-level medium as an effective two-level configuration

2021 ◽  
Vol 51 (2) ◽  
Author(s):  
Jihad S. Addasi
Keyword(s):  
Energy Levels ◽  
Total Probability ◽  
Nonlinear Processes ◽  
Effective Population ◽  
Complex Molecules ◽  
Excited Triplet ◽  
Channel Ratio ◽  
Saturation Intensity ◽  
Effective Level ◽  
Level Medium

Saturation of complex molecules affects the nonlinear processes occurring in the medium. The medium can be described by two-, three-, and four-level configurations. The principal singlet-singlet and excited triplet-triplet channels of a four-level, N-type, configuration were used to study a nonlinear medium, which was excited by radiation with two frequencies. Under weak population of energy levels in the triplet-triplet channel (a small ratio of the total probability of spontaneous and irradiate transitions for both channels p23/p31), the principal (singlet-singlet) channel is similar to a two-level configuration. At the same time, the effective population of the energy levels in the triplet-triplet channel (the ratio p23/p31 is large and the radiation intensity in the principal channel is high) makes the excited (triplet-triplet) channel coincide with the two-level configuration. The saturation intensity of radiation in principal (excited) channel, as effective two-level configuration, and nonlinear processes in this channel can be controlled by external radiation acting on excited (principal) channel. Finally, the average excitation of molecules into the energy levels in the triplet-triplet channel (ratio p23/p31 ≈ 1) makes the four-level configuration similar to the three-level configuration with effective level as a result of combination between second singlet level S2 and first triplet level T1.

A spectroscopic study of HCP, the phosphorus analogue of hydrocyanic acid

1969 ◽  
Vol 47 (8) ◽  
pp. 893-920 ◽  
Author(s):  
J. W. C. Johns ◽  
H. F. Shurvell ◽  
J. K. Tyler
Keyword(s):  
Energy Levels ◽  
Hydrocyanic Acid ◽  
Ultraviolet Absorption Spectrum ◽  
Triplet States ◽  
Fundamental Vibration ◽  
Excited Triplet ◽  
Singlet States ◽  
State Formula ◽  
Excited Singlet States ◽  
Vibration Rotation

The ultraviolet absorption spectrum of HCP has been observed from 4100 Å to about 2350 Å, and seven electronic transitions have been identified. Three of these transitions involve excited singlet states and four of them involve excited triplet states. The symmetries, energies, and equilibrium conformations of these states are listed below:[Formula: see text]Some observations have also been made on the vibration–rotation energy levels of the ground electronic state, [Formula: see text], of HCP. The fundamental vibration frequencies (in cm−1) are ν1 = 3216.9, ν2 = 674.7, and ν3 = 1278.4.

scholarly journals The ALMA-PILS Survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293–2422 B

2018 ◽  
Vol 610 ◽  
pp. A54 ◽  
Author(s):  
M. V. Persson ◽  
J. K. Jørgensen ◽  
H. S. P. Müller ◽  
A. Coutens ◽  
E. F. van Dishoeck ◽  
...  
Keyword(s):  
Energy Levels ◽  
Excitation Temperature ◽  
Thermodynamical Equilibrium ◽  
Complex Molecules ◽  
Important Species ◽  
Chemical Models ◽  
Small Scales ◽  
Core Phase ◽  
Low Mass ◽  
First Time

Context.The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. Formaldehyde is an important species in the formation of methanol and more complex molecules.Aims.Here, we aim to present the first study of formaldehyde deuteration on small scales around the prototypical low-mass protostar IRAS 16293–2422 using high spatial and spectral resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations. We determine the excitation temperature, abundances and fractionation level of several formaldehyde isotopologues, including its deuterated forms.Methods.Excitation temperature and column densities of formaldehyde in the gas close to one of the components of the binary were constrained through modeling of optically thin lines assuming local thermodynamical equilibrium. The abundance ratios were compared to results from previous single dish observations, astrochemical models and local ISM values.Results.Numerous isotopologues of formaldehyde are detected, among them H2C17O, and D213CO for the first time in the ISM. The large range of upper energy levels covered by the HDCO lines help constrain the excitation temperature to 106 ± 13 K. Using the derived column densities, formaldehyde shows a deuterium fractionation of HDCO/H2CO = 6.5 ± 1%, D2CO/HDCO = 12.8–4.1+3.3%, and D2CO/H2CO = 0.6(4) ± 0.1%. The isotopic ratios derived are16O/18O = 805–79+43,18O/17O = 3.2–0.3+0.2, and12C/13C = 56–11+8.Conclusions.The HDCO/H2CO ratio is lower than that found in previous studies, highlighting the uncertainties involved in interpreting single dish observations of the inner warm regions. The D2CO/HDCO ratio is only slightly larger than the HDCO/H2CO ratio. This is consistent with formaldehyde forming in the ice as soon as CO has frozen onto the grains, with most of the deuteration happening toward the end of the prestellar core phase. A comparison with available time-dependent chemical models indicates that the source is in the early Class 0 stage.

Energy Levels of Oligothiophenes in the Higher Excited Triplet States

2007 ◽  
Vol 111 (2) ◽  
pp. 1024-1028 ◽  
Author(s):  
Yosuke Oseki ◽  
Mamoru Fujitsuka ◽  
Masanori Sakamoto ◽  
Xichen Cai ◽  
Tetsuro Majima
Keyword(s):  
Energy Levels ◽  
Triplet States ◽  
Excited Triplet ◽  
Excited Triplet States

scholarly journals Methanol formation in TW Hya and future prospects for detecting larger complex molecules in disks with ALMA

2017 ◽  
Vol 13 (S332) ◽  
pp. 395-402 ◽  
Author(s):  
Catherine Walsh ◽  
Shreyas Vissapragada ◽  
Harry McGee
Keyword(s):  
Gas Phase ◽  
Signal To Noise Ratio ◽  
Energy Levels ◽  
Complex Molecules ◽  
Rotational Spectra ◽  
Chemical Models ◽  
Methanol Formation ◽  
Peak Abundance ◽  
Abundance And Distribution ◽  
First Time

AbstractGas-phase methanol was recently detected in a protoplanetary disk for the first time with ALMA. The peak abundance and distribution of methanol observed in TW Hya differed from that predicted by chemical models. Here, the chemistry of methanol gas and ice is calculated using a physical model tailored for TW Hya with the aim to contrast the results with the recent detection in this source. New pathways for the formation of larger complex molecules (e.g., ethylene glycol) are included in an updated chemical model, as well as the fragmentation of methanol ice upon photodesorption. It is found that including fragmentation upon photodesorption improves the agreement between the peak abundance reached in the chemical models with that observed in TW Hya (∼10−11 with respect to H2); however, the model predicts that the peak in emission resides a factor of 2 − 3 farther out in the disk than the ALMA images. Reasons for the persistent differences in the gas-phase methanol distribution between models and the observations of TW Hya are discussed. These include the location of the ice reservoir which may coincide with the compact mm-dust disk (≲ 60 au) and sources of gas-phase methanol which have not yet been considered in models. The possibility of detecting larger molecules with ALMA is also explored. Calculations of the rotational spectra of complex molecules other than methanol using a parametric model constrained by the TW Hya observations suggest that the detection of individual emission lines of complex molecules with ALMA remains challenging. However, the signal-to-noise ratio can be enhanced via stacking of multiple transitions which have similar upper energy levels.

A new target configuration producing an effective population inversion at energy levels of Mg XI 1s3p and 1s4p

1988 ◽  
Vol 65 (6) ◽  
pp. 445-451 ◽  
Author(s):  
Zunqi Lin ◽  
Wenyan Yu ◽  
Weihan Tan ◽  
Wenhua Chen ◽  
Yuxia Zheng ◽  
...  
Keyword(s):  
Population Inversion ◽  
Energy Levels ◽  
Effective Population ◽  
Target Configuration

scholarly journals Селективное возбуждение и создание инверсной населенности в квантовых системах с помощью униполярных аттосекундных и терагерцовых импульсов

2020 ◽  
Vol 128 (12) ◽  
pp. 1905
Author(s):  
Р.М. Архипов ◽  
М.В. Архипов ◽  
А.В. Пахомов ◽  
М.О. Жукова ◽  
А.Н. Цыпкин ◽  
...  
Keyword(s):  
Strong Field ◽  
Energy Levels ◽  
Weak Field ◽  
Quantum Systems ◽  
Spatial Profile ◽  
Terahertz Pulses ◽  
Selective Population ◽  
Dynamics Of Population ◽  
The Impact ◽  
Level Medium

The possibility of selective population of the energy levels of quantum systems was studied using a single unipolar subcycle pulse and a pair of pulses. Selective population of quantum levels is clearly illustrated based on the numerical solution of the system of equations for the density matrix of a three-level medium interacting with a pair of subcycle attosecond and terahertz pulses. The possibility of creating an population inversion in a three-level medium is shown using a pair of such pulses. The dynamics of population density gratings in a three-level medium is studied at the impact on the system of a pair of large-amplitude Gaussian pulses. If in a weak field the shape of the gratings is harmonic, according to analytical calculations performed according to perturbation theory, then in in the case of a strong field, the spatial profile of the gratings can differ from the sinusoidal one and has complex spike structure.

Zusammenhang zwischen Schweratominduzierter Fluoreszenzlöschung und Termschema von mehrkernigen aromatischen Kohlenwasserstoffen / Correlation between Heavy-atom induced Fluorescence Quenching and Energy Levels of Polynuclear Aromatic Hydrocarbons

1973 ◽  
Vol 28 (10) ◽  
pp. 1743-1744
Author(s):  
H. Dreeskamp ◽  
M. Zander
Keyword(s):  
Aromatic Hydrocarbons ◽  
Energy Gap ◽  
Energy Levels ◽  
Heavy Atom ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Excited Triplet ◽  
Wide Energy ◽  
Excited Triplet States

The observation that the fluorescence of certain polynuclear aromatic hydrocarbons (perylene, 1.2 ;5.6-dibenzoperylene, 9.10-diphenylanthracene and rubrene) is quenched by alkyl iodides only slightly is explained on the basis of the energy levels of these hydrocarbons. In these systems an effective radiationless desactivation of the fluorescing state S1 by intersystem crossing into the triplet manifold is prevented by a wide energy gap between S1 and the lowest triplet state, and the absence of excited triplet states below s,.

scholarly journals Генерация предельно коротких импульсов терагерцового излучения на основе сверхизлучения трехуровневой резонансной среды

2021 ◽  
Vol 129 (3) ◽  
pp. 319
Author(s):  
Р.М. Архипов ◽  
Н.Н. Розанов
Keyword(s):  
Thin Layer ◽  
Energy Levels ◽  
Resonant Medium ◽  
Thz Radiation ◽  
Quantum Harmonic Oscillator ◽  
Terahertz Pulse ◽  
Nonlinear Polarization ◽  
Short Pulses ◽  
Superradiance Pulse ◽  
Level Medium

The possibility of generating extremely short pulses of terahertz (THz) radiation due to superradiance - collective spontaneous emission of stopped polarization of a thin layer of a three-level resonant medium excited by a pair of attosecond (or femtosecond) pulses is studied theoretically. The source of a terahertz pulse is a pulse of stopped nonlinear polarization of the medium, which occurs in the interval between its excitation and de-excitation. The case of a three-level medium with equidistant energy levels (as in a quantum harmonic oscillator), the transition frequency of which lies in the THz range, is considered. The influence of the populations of the excited levels of the medium on the shape of the terahertz superradiance pulse is discussed.

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