Browsing by Author "Chandra, Suresh"

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Anomalous absorption in thioformaldehyde
(2009-10-01) Chandra, Suresh; Kumar, Amit; Sharma, M. K.
Absorption against the Cosmic Microwave Background (CMB), called the anomalous absorption, is an unusual phenomenon. The transition 111 110 at 4.829 GHz of formaldehyde (H2CO) was the rst one showing the anomalous absorption. The c-C3H2 is the second molecule showing anomalous absorption through its transition 220 211 at 21.590 GHz. Structure of thioformaldehyde (H2CS) is very similar to that of the H2CO. Therefore, we have investigated about the physical conditions under which the transition 111 110 at 1.0465 GHz of H2CS would be found in anomalous absorption in cool cosmic objects. As in case of H2CO, the anomalous absorption of 111 110 of H2CS is found sensitive to the relative collisional rates and it requires that the collisional rate for the transition 111 211 must be smaller than that for the transition 110 212.
Anomalous obsorption in H2Co molecule
(2005-12-01) Chandra, Suresh; Musrif, P. G.; Shinde, S. V.
Collisional transitions in interstellar asymmetric top molecules
(2011-11-22) Chandra, Suresh
Detection of rotational lines of NaSH molecule
(2001-07-02) Sharma, A. K.; Chandra, Suresh
MHD modes of solar wind flow tubes
(2008-02) Chandra, Suresh
Nakariakov & Roberts (1995) and Nakariakov et al. (1996) investigated the linear mag- netosonic waves trapped within solar wind ow tubes by accounting for a slab having boundaries at x = d and extended up to in nity in y and z directions. They obtained dispersion relations for sausage and kink surface waves in incompressible plasma. Following the approach of Nakariakov & Roberts (1995), we have obtained dispersion relations for sausage and kink surface waves in a compressible plasma. Values of the parameter a !=kCAo are found to vary in the ranges 0.755 0.849 and 1.080 1.356 for the sausage waves and in the ranges 0.850 0.882 and 1.358 1.538 for the kink waves in the compressible plasma. It shows an interesting feature that the sausage and kink surface waves are exclusive from each other.
On temperature T01 for molecular hydrogen
(2011-07-06) Chandra, Suresh
Abstract: Temperature TOl for hydrogen molecule for the transition between the level J = 1 (ortho-Hj) and the level J = 0 (para-He) has been introduced by Spitzer et al. [1]. The work of Spitzer et al. [1]has been reinvestigated and we find that the concept of the temperature TOl is not valid.
Search for an interstellar Si2C molecule: A theoretical prediction
(2011-07-06) Chandra, Suresh
We suggest that Si2C molecule may be identi¯ed in astronomical objects through its transitions 414 ! 505, 515 ! 606, 212 ! 303, 313 ! 404, and 111 ! 202 at 15.9, 5.1, 33.6, 24.9, and 42.3 GHz in absorption even against the cosmic 2.7 K background, in a region having low temperature. The absorption phenomenon is found rather large in the ¯rst two transitions. Dependence of results on the set of molecular parameters is discussed.
Suggesions for an interstellar C5H2 search
(2011-07-06) Chandra, Suresh; Shinde, S. A.
Laboratory detection of four isomers of C5H2 molecule have been reported by Travers et al. (1997), McCarthy et al. (1997), and Gottlieb et al. (1998). They suggested for detection of the ring-chain isomer of C5H2 (c-C5H2)incosmic objects, as it is the most stable one in comparison to the others. Two transitions 313−212 and 303−202 at 19.147 GHz and 19.606 GHz, respectively, of c-C5H2 have been detected in TMC-1. We suggest that the c-C5H2 may be identiﬁed in cool cosmic objects through its transition 313−404 at 4.3 GHz in absorption against the cosmic microwave background. Since in absence of availability of the collisional rates, we have used scaled values for them, we have checked the sensitivity of the lines on the rates by enhancing the rate for the transitions with ∆ka = 0 by a factor of 10. Though the transitions are not found sensitive, our results may be treated as qualitative in nature. This absorption line may play an important role for identiﬁcation of c-C5H2 in cosmic objects.
Suggestions for an interstellar C7H2 Search
(2011-07-06) Chandra, Suresh; Musrif, P. G.; Dharmkare, Ram M.
Laboratory detection of the ring-chain molecule c-C7H2 has been reported by McCarthy et al. [McCarthy, M.C., Travers, M.J., Gottlieb, C.A., Thaddeus, P., 1997. A&A 483, L139]. Two ring-chain molecules c-C3H2 and c-C5H2 of this series have already been detected in the cosmic objects. We suggest that the c-C7H2 may be identiﬁed in cool cosmic objects through its transitions 414–505,515–606,616–707 and 717–808 at 23.241, 21.105, 18.953 and 16.787 GHz, respectively, in absorption against the CMB. Since, in absence of the availability of collisional rates, we have used scaled values for them, we have checked the sensitivity of the results on the collisional rates, by enhancing the rates for the transitions with Dka = 0 by a factor of 10. Though the transitions are not found sensitive to the collisional rates, our results still may be treated as qualitative in nature. These absorption lines may play an important role for identiﬁcation of c-C H in cool cosmic objects.