• 자연과학논문집
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• 제12권1호
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• pp.23-30
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• 2002

원자와 빛과의 상호작용에 의해 원자의 결맞음이 유도될 수 있는데, 이러한 원자의 결맞음은 새로운 물성 및 광학적 현상을 제공한다. 2광자 공진은 원자의 결맞음 형성에 중요한 역할을 하는데 지금까지 2광자 조건에 대한 근사적인 공식이 사용되어져 왔다. 본 논문에서는 2광자 공진 조건을 정확히 유도하고, 수치적 계산을 통하여 이를 확인하였으며, 주파수 편이 및 빛의 세기에 따른 2광자 공진 조건의 변화를 조사하였다.

• Bulletin of the Korean Chemical Society
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• 제21권7호
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• pp.712-714
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• 2000

Non-Lorentyian resonance is predicted to occur in two-photon photoabsorption processes due to the detuning off the intermediate levels. This type of non-Lorentzian resonance is distinct from the asymmetric resonance resulting from the effects of q uantum interference between competing indistinguishable dynamic pathways. The product distributions are shown to be constant near this type of resonance.

• 한국광학회:학술대회논문집
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• 한국광학회 1991년도 광학 및 양자전자학 워크샵
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• pp.15-22
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• 1991

The general aspects of Laser Resonance Ionization Spectroscopy (RIS) and its application are investigated. Combination of laser selective photoionization and mass spectrometer as apromising spectroscopic as well as an analytical tool is mainly considered. The application of RIS includes mercury (Hg) atomic spectroscopy, trace analysis of lead (Pb) and resonance enhanced two photon ionization spectroscopy of Cis-hexatriene.

• Journal of the Optical Society of Korea
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• 제7권2호
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• pp.119-125
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• 2003

We demonstrate parametric resonance in a magneto-optical trap. When we modulate the intensity of the cooling laser at about twice the resonant frequency of the trap, the atoms in the trap are divided into two parts and oscillate with 180 degree phase difference with the finite length due to nonlinearity of the trap potential. These are the effects of general nonlinear dynamics, called the Hopf bifurcation, or limit cycle motion. The amplitude and the phase of the oscillations are measured and compared with the theoretical calculations based on simple Doppler cooling theory. The experimental results are in excellent agreement with the simulation results based on the simple Doppler cooling theory.

• 대한화학회지
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• 제36권6호
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• pp.832-839
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• 1992

Time-of-Flight(TOF) 질량분석기가 설치된 분광분석장치를 이용하여 레이저 공명이온화 분광법으로 극미량의 납을 정량하였다. 납에 대한 극미량 분석을 위해 단색 2광자 공명이온화, 2색 2광자 공명이온화 및 3색 3광자 공명 이온화의 세 가지 광이온화 경로가 시도되었다. 이 때, 첫번째 들뜬 준위는 바닥준위로부터 283.3 nm의 파장에 해당하는 6p7s($^3P_1$)준위를 공통적으로 사용하였다. 이들 이온화경로를 통해 여러가지 농도의 납 표준용액을 사용하여 0.1 ${\mu}g$에서 1pg의 영역에 해당하는 검정곡선을 얻었다. 검정곡선으로부터 얻은 본 분석법의 검출한계는 2색 2광자 공명이온화 및 3색 3광자 공명이온화의 경우 각각 20 및 10pg 이었다. 또한 각각의 이온화 경로에 따른 이온화 효율도 함께 비교 검토하였다.

• Bulletin of the Korean Chemical Society
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• 제16권7호
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• pp.578-582
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• 1995

The resonance ionization mass spectrometry (RIMS) system with angular reflectron type time-of-flight mass spectrometer (AREF-TOFMS) has been developed and characterized. The system is applied for the ultratrace determination of Pb element. The 2-color 3-photon laser ionization scheme is adopted for the study and the mass resolution of the system is determined as T/ΔT=1680. The calibration curve for Pb is obtained in the range of 100 ppb to 0.01 ppb by using standard solutions. The minimal amount of detection for the present RIMS system is determined as less than 100 femtograms (10-13 gram).

• ETRI Journal
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• 제23권3호
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• pp.106-110
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• 2001

Subpicosecond all-optical switching method based on the simultaneous two-photon coherence exchange is proposed and numerically demonstrated. The optical switching mechanism is based on the optical field induced dark resonance swapping via nondegenerate four-wave mixing processes. For potential applications of ultrafast all-optical switching in fiber-optic communications, 10-THz channel number independent quantum router is discussed.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.179-183
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• 2002

Resonance-enhanced multiphoton ionization with time-of-flight product imaging of the $N(^2D)$ atoms has been used to study the $N_2O$ photodissociation at 118.2 nm and the two-photon dissociation at 268.9 nm. These imaging experiments allowed the determination of the total kinetic energy distribution of the $NO(X^2{\prod})$ and $N(^2D_{5/2})$ products. The $NO(X^2{\prod})$ fragments resulting from the photodissociation processes are produced in highly vibrationally excited states. The two-photon photodissociation process yields a broad $NO(X^2{\prod})$ vibrational energy distribution, while the 118.2 nm dissociation appears to produce a vibrational distribution sharply peaked at $NO(X^2{\prod},\;{\nu}=14)$.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.189-194
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• 2002

Two-photon resonant third photon ionization of atomic bromine $(4p^5\;^2P_{3/2}\;and\;^2P_{1/2})$ has been studied using a photoelectron imaging spectroscopy in the wavelength region 250 - 278 nm. The technique has yielded simultaneously both relative branching ratios to the three levels of $Br^+(^3P_2,\;^3P_{0.1}\;and^1D_2)$ with $4p^4$ configuration and the angular distributions of outgoing photoelectrons. The product branching ratios reveal a strong propensity to populate particular levels in many cases. Several pathways have been documented for selective formation of $Br^+(^3P_2)$ and $Br^+(^3P_{0.1})$ ions. In general, the final ion level distributions are dominated by the preservation of the ion core configuration of a resonant excited state. Some deviations from this simple picture are discussed in terms of the configuration interaction of resonant states and the autoionization in the continuum. The photoelectron angular distributions are qualitatively similar for all transitions, with a positive $A_2$ anisotropy coefficient of 1.0-2.0 and negligible $A_4$ in most cases, which suggests that the angular distribution is mainly determined by the single-photon ionization process of a resonant excited state induced from the third photon absorption.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.267-270
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• 2002

Photodissociations of o-, m-, and p-iodotoluene radical cations were investigated by using Fourier-transform ion cyclotron resonance (FT-ICR) spectrometry. Iodotoluene radical cations were prepared in an ICR cell by a photoionization charge-transfer method. The time-resolved one-photon dissociation spectra were obtained at 532 nm and the identities of $C_7H_7^+$ products were determined by examining their bimolecular reactivities toward toluene-$d_8$. The two-photon dissociation spectra were also recorded in the wavelength range 615-670 nm. The laser power dependence, the temporal variation, and the identities of $C_7H_7^+$ were examined at 640 nm. The mechanism of unimolecular dissociation of iodotoluene radical cations is elucidated: the lowest barrier rearrangement channel leads exclusively to the formation of the benzyl cation, whereas the direct C-I cleavage channel yields the tolyl cations that rearrange to both benzyl and tropylium cations with dissimilar branching ratios among o-, m-, and p-isomers. With a two-photon energy of 3.87 eV at 640 nm, the direct C-I cleavage channel results in the product branching ratio, [tropylium cation]/[benzyl cation], in descending order, 0.16 for meta >0.09 for ortho >0.05 for para.