A double resonance action spectroscopic method has been applied to measure low-J rotational transitions of H2D+ and D2H+ up to frequencies of 1.5 THz. The uncertainties of two known lines of H2D+ and three known lines of D2H+ have been improved substantially, and the 211←212 H2D+ transition measured for the first time. In addition, we derived spectroscopic parameters for both molecular cations using the Euler formalism. © 2016 Elsevier Inc.

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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.

Journal	Journal of Molecular Spectroscopy
Publisher	Academic Press Inc.
ISSN	0022-2852