The line shape calculation of a weak microwave signal in the presence of a strong radio frequency pump shows that the Bloch-Siegert shift of the pump resonance frequency can produce a shift and asymmetry of the Rabi frequency components of the signal for on-resonance pumping. © 1992.

S MANDAL

P N GHOSH

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Bloch—Siegert effect in three-level rfmw double resonance

Chemical Physics Letters

The interaction of two electromagnetic radiations with a four-level atom with two closely spaced common levels is studied for the cascade system. The spacing between the close levels is assumed to be small so that the radiation frequency can act simultaneously on the two closely spaced resonances. Fifteen Bloch equations are developed for the four-level atom and a computer program is written for their solution in the steady state. Numerical computations for the line shape of the signal having the closely spaced levels at the lower level and a single upper level are reported. The closely spaced levels are the upper levels for the pump transition. When the signal is on-resonance with one of the transitions, a Rabi splitting is observed, but the presence of a nearby transition produces an asymmetry between the Rabi components. The asymmetry depends on the transition moment of the nearby transition and disappears when the other transition is weak. In the case of off-resonance pumping a weak two-photon signal is found in addition to the two signals. The intensity of the two-photon signal depends on the pump radiation frequency. © 1992.

Spectrochimica Acta Part A: Molecular Spectroscopy

Signal line shapes in four-level double resonance spectroscopy with closely spaced levels

The lineshape of a pair of Doppler-free closely spaced transitions sharing a common level in the presence of a uniform radiation field is studied by solving the coupled optical Bloch equations numerically. It is shown that the non-linear term corresponding to the product of the two transition dipoles and the density matrix element connecting the closely spaced upper levels broadens the lineshape and shifts the peak frequency positions. © 1989.

Lineshape theory of doppler-free coupled closely spaced transitions in the presence of a strong radiation field: The effect of non-resonant interactions

A set of coupled optical Bloch equations has been solved to obtain the absorption lineshape for both copropagating and counterpropagating three-level double resonances in the presence of a strong infrared laser source. The resonance conditions and lineshapes derived for the Lamb dip and three-level double resonances are confirmed by recent experimental findings in 15NH3. © 1986.

Lineshape theory for three-level double resonance in the presence of infrared laser radiation

A theory of line shape for a Doppler broadened probe in the presence of a strong infrared pump is presented. The optical analog of Bloch equations has been developed; the T1, T2 relaxations are introduced phenomenologically in these equations. Doppler broadening of both the pump and signal transitions are taken into account to obtain the absorption coefficient for the signal. This leads to a Doppler broadened Gaussian function weighted by a pump induced Lorentzian function whose position and linewidth are controlled by the detuning and power respectively of the pump radiation. The absorption coefficient is further modulated by a Lorentzian function containing the fourth power of the radiation. The off-resonance pumping leads to two symmetrically located "Lamb dips" or "peaks" around the Gaussian pedestal for co- and counter propagating laser radiations. A calculation of the line shape of the central sub-Doppler feature for the on-resonance pumping is in good agreement with the observed variation of linewidth with pressure. Numerical results are presented graphically to demonstrate the pump and signal power dependence of the central hole or peak for the bent and cascade-type double resonances. The results obtained confirm the expected behavior based on level populations. © 1985 American Institute of Physics.

Journal	Chemical Physics Letters
Publisher	-
ISSN	0009-2614