We report observations of methanol emission at 84-GHz toward 32 infrared dark cloud (IRDC) sources at various evolutionary stages. Data were obtained using the 20-meter radiotelescope located in Onsala, Sweden, during 2019-2020. Among these 32 sources, the 5$_{-1}$---4$_{0} E$ methanol emission was detected in 24. These objects do not overlap with any previously observed 84-GHz sources, making all our detections novel. Based on our findings, five sources were identified in which emission of class I methanol masers was observed. Additionally, we compare the 84-GHz observations with previous 44-GHz measurements toward the same sources, revealing a correlation between emission at both frequencies and notable similarities in their spectral profiles.
33.20.Bx Radio-frequency and microwave spectra
95.75.Fg Spectroscopy and spectrophotometry
97.10.Bt Star formation
$^1$Astro Space Center, P.N. Lebedev Physical Institute of the Russian Academy of Sciences
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